/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.util;

import java.io.Closeable;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.net.URI;
import java.nio.file.FileSystem;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.Permission;
import java.security.PermissionCollection;
import java.security.Permissions;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.security.ProtectionDomain;
import java.security.SecurityPermission;
import java.text.Collator;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Random;
import java.util.Set;
import java.util.TimeZone;
import java.util.TreeSet;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.logging.Logger;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.MockAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field.Store;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.FieldType;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.*;
import org.apache.lucene.index.TermsEnum.SeekStatus;
import org.apache.lucene.mockfile.FilterPath;
import org.apache.lucene.mockfile.VirusCheckingFS;
import org.apache.lucene.search.AssertingIndexSearcher;
import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.LRUQueryCache;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.QueryCache;
import org.apache.lucene.search.QueryCachingPolicy;
import org.apache.lucene.store.BaseDirectoryWrapper;
import org.apache.lucene.store.ByteBuffersDirectory;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.store.FSLockFactory;
import org.apache.lucene.store.FileSwitchDirectory;
import org.apache.lucene.store.FlushInfo;
import org.apache.lucene.store.IOContext;
import org.apache.lucene.store.LockFactory;
import org.apache.lucene.store.MMapDirectory;
import org.apache.lucene.store.MergeInfo;
import org.apache.lucene.store.MockDirectoryWrapper.Throttling;
import org.apache.lucene.store.MockDirectoryWrapper;
import org.apache.lucene.store.NRTCachingDirectory;
import org.apache.lucene.store.RawDirectoryWrapper;
import org.apache.lucene.util.automaton.AutomatonTestUtil;
import org.apache.lucene.util.automaton.CompiledAutomaton;
import org.apache.lucene.util.automaton.RegExp;
import org.junit.After;
import org.junit.AfterClass;
import org.junit.Assert;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.ClassRule;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.RuleChain;
import org.junit.rules.TestRule;
import org.junit.runner.RunWith;
import org.junit.internal.AssumptionViolatedException;

import com.carrotsearch.randomizedtesting.JUnit4MethodProvider;
import com.carrotsearch.randomizedtesting.LifecycleScope;
import com.carrotsearch.randomizedtesting.MixWithSuiteName;
import com.carrotsearch.randomizedtesting.RandomizedContext;
import com.carrotsearch.randomizedtesting.RandomizedRunner;
import com.carrotsearch.randomizedtesting.RandomizedTest;
import com.carrotsearch.randomizedtesting.annotations.Listeners;
import com.carrotsearch.randomizedtesting.annotations.SeedDecorators;
import com.carrotsearch.randomizedtesting.annotations.TestGroup;
import com.carrotsearch.randomizedtesting.annotations.TestMethodProviders;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakAction.Action;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakAction;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakFilters;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakGroup.Group;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakGroup;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakLingering;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakScope.Scope;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakScope;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakZombies.Consequence;
import com.carrotsearch.randomizedtesting.annotations.ThreadLeakZombies;
import com.carrotsearch.randomizedtesting.annotations.TimeoutSuite;
import com.carrotsearch.randomizedtesting.generators.RandomPicks;
import com.carrotsearch.randomizedtesting.rules.NoClassHooksShadowingRule;
import com.carrotsearch.randomizedtesting.rules.NoInstanceHooksOverridesRule;
import com.carrotsearch.randomizedtesting.rules.StaticFieldsInvariantRule;

import junit.framework.AssertionFailedError;

import static com.carrotsearch.randomizedtesting.RandomizedTest.systemPropertyAsBoolean;
import static com.carrotsearch.randomizedtesting.RandomizedTest.systemPropertyAsInt;
import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;

/**
 * Base class for all Lucene unit tests, Junit3 or Junit4 variant.
 * 
 * <h3>Class and instance setup.</h3>
 * 
 * <p>
 * The preferred way to specify class (suite-level) setup/cleanup is to use
 * static methods annotated with {@link BeforeClass} and {@link AfterClass}. Any
 * code in these methods is executed within the test framework's control and
 * ensure proper setup has been made. <b>Try not to use static initializers
 * (including complex final field initializers).</b> Static initializers are
 * executed before any setup rules are fired and may cause you (or somebody 
 * else) headaches.
 * 
 * <p>
 * For instance-level setup, use {@link Before} and {@link After} annotated
 * methods. If you override either {@link #setUp()} or {@link #tearDown()} in
 * your subclass, make sure you call <code>super.setUp()</code> and
 * <code>super.tearDown()</code>. This is detected and enforced.
 * 
 * <h3>Specifying test cases</h3>
 * 
 * <p>
 * Any test method with a <code>testXXX</code> prefix is considered a test case.
 * Any test method annotated with {@link Test} is considered a test case.
 * 
 * <h3>Randomized execution and test facilities</h3>
 * 
 * <p>
 * {@link LuceneTestCase} uses {@link RandomizedRunner} to execute test cases.
 * {@link RandomizedRunner} has built-in support for tests randomization
 * including access to a repeatable {@link Random} instance. See
 * {@link #random()} method. Any test using {@link Random} acquired from
 * {@link #random()} should be fully reproducible (assuming no race conditions
 * between threads etc.). The initial seed for a test case is reported in many
 * ways:
 * <ul>
 *   <li>as part of any exception thrown from its body (inserted as a dummy stack
 *   trace entry),</li>
 *   <li>as part of the main thread executing the test case (if your test hangs,
 *   just dump the stack trace of all threads and you'll see the seed),</li>
 *   <li>the master seed can also be accessed manually by getting the current
 *   context ({@link RandomizedContext#current()}) and then calling
 *   {@link RandomizedContext#getRunnerSeedAsString()}.</li>
 * </ul>
 */
@RunWith(RandomizedRunner.class)
@TestMethodProviders({
  LuceneJUnit3MethodProvider.class,
  JUnit4MethodProvider.class
})
@Listeners({
  RunListenerPrintReproduceInfo.class,
  FailureMarker.class
})
@SeedDecorators({MixWithSuiteName.class}) // See LUCENE-3995 for rationale.
@ThreadLeakScope(Scope.SUITE)
@ThreadLeakGroup(Group.MAIN)
@ThreadLeakAction({Action.WARN, Action.INTERRUPT})
@ThreadLeakLingering(linger = 20000) // Wait long for leaked threads to complete before failure. zk needs this.
@ThreadLeakZombies(Consequence.IGNORE_REMAINING_TESTS)
@TimeoutSuite(millis = 2 * TimeUnits.HOUR)
@ThreadLeakFilters(defaultFilters = true, filters = {
    QuickPatchThreadsFilter.class
})
@TestRuleLimitSysouts.Limit(
    bytes = TestRuleLimitSysouts.DEFAULT_LIMIT,
    hardLimit = TestRuleLimitSysouts.DEFAULT_HARD_LIMIT)
public abstract class LuceneTestCase extends Assert {

  // --------------------------------------------------------------------
  // Test groups, system properties and other annotations modifying tests
  // --------------------------------------------------------------------

  public static final String SYSPROP_NIGHTLY = "tests.nightly";
  public static final String SYSPROP_WEEKLY = "tests.weekly";
  public static final String SYSPROP_MONSTER = "tests.monster";
  public static final String SYSPROP_AWAITSFIX = "tests.awaitsfix";
  public static final String SYSPROP_SLOW = "tests.slow";
  public static final String SYSPROP_BADAPPLES = "tests.badapples";

  /** @see #ignoreAfterMaxFailures*/
  public static final String SYSPROP_MAXFAILURES = "tests.maxfailures";

  /** @see #ignoreAfterMaxFailures*/
  public static final String SYSPROP_FAILFAST = "tests.failfast";

  /**
   * Annotation for tests that should only be run during nightly builds.
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @TestGroup(enabled = false, sysProperty = SYSPROP_NIGHTLY)
  public @interface Nightly {}

  /**
   * Annotation for tests that should only be run during weekly builds
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @TestGroup(enabled = false, sysProperty = SYSPROP_WEEKLY)
  public @interface Weekly {}
  
  /**
   * Annotation for monster tests that require special setup (e.g. use tons of disk and RAM)
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @TestGroup(enabled = false, sysProperty = SYSPROP_MONSTER)
  public @interface Monster {
    String value();
  }

  /**
   * Annotation for tests which exhibit a known issue and are temporarily disabled.
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @TestGroup(enabled = false, sysProperty = SYSPROP_AWAITSFIX)
  public @interface AwaitsFix {
    /** Point to JIRA entry. */
    public String bugUrl();
  }

  /**
   * Annotation for tests that are slow. Slow tests do run by default but can be
   * disabled if a quick run is needed.
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @TestGroup(enabled = true, sysProperty = SYSPROP_SLOW)
  public @interface Slow {}

  /**
   * Annotation for tests that fail frequently and are not executed in Jenkins builds
   * to not spam mailing lists with false reports.
   *
   * Tests are turned on for developers by default. If you want to disable
   * them, set:
   * <pre>
   * -Dtests.badapples=false
   * </pre>
   * (or do this through {@code ~./lucene.build.properties}).
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @TestGroup(enabled = true, sysProperty = SYSPROP_BADAPPLES)
  public @interface BadApple {
    /** Point to JIRA entry. */
    public String bugUrl();
  }

  /**
   * Annotation for test classes that should avoid certain codec types
   * (because they are expensive, for example).
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.TYPE)
  public @interface SuppressCodecs {
    String[] value();
  }
  
  /**
   * Annotation for test classes that should avoid mock filesystem types
   * (because they test a bug that only happens on linux, for example).
   * <p>
   * You can avoid specific names {@link Class#getSimpleName()} or use
   * the special value {@code *} to disable all mock filesystems.
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.TYPE)
  public @interface SuppressFileSystems {
    String[] value();
  }
  
  /**
   * Annotation for test classes that should avoid always omit
   * actual fsync calls from reaching the filesystem.
   * <p>
   * This can be useful, e.g. if they make many lucene commits.
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.TYPE)
  public @interface SuppressFsync {}
  
  /**
   * Marks any suites which are known not to close all the temporary
   * files. This may prevent temp. files and folders from being cleaned
   * up after the suite is completed.
   * 
   * @see LuceneTestCase#createTempDir()
   * @see LuceneTestCase#createTempFile(String, String)
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.TYPE)
  public @interface SuppressTempFileChecks {
    /** Point to JIRA entry. */
    public String bugUrl() default "None";
  }

  /**
   * Ignore {@link TestRuleLimitSysouts} for any suite which is known to print 
   * over the default limit of bytes to {@link System#out} or {@link System#err}.
   * 
   * @see TestRuleLimitSysouts
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.TYPE)
  public @interface SuppressSysoutChecks {
    /** Point to JIRA entry. */
    public String bugUrl();
  }

  /**
   * Suppress the default {@code reproduce with: ant test...}
   * Your own listener can be added as needed for your build.
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.TYPE)
  public @interface SuppressReproduceLine {}
  
  // -----------------------------------------------------------------
  // Truly immutable fields and constants, initialized once and valid 
  // for all suites ever since.
  // -----------------------------------------------------------------

  /**
   * True if and only if tests are run in verbose mode. If this flag is false
   * tests are not expected to print any messages. Enforced with {@link TestRuleLimitSysouts}.
   */
  public static final boolean VERBOSE = systemPropertyAsBoolean("tests.verbose", false);

  /**
   * Enables or disables dumping of {@link InfoStream} messages. 
   */
  public static final boolean INFOSTREAM = systemPropertyAsBoolean("tests.infostream", VERBOSE);

  /**
   * A random multiplier which you should use when writing random tests:
   * multiply it by the number of iterations to scale your tests (for nightly builds).
   */
  public static final int RANDOM_MULTIPLIER = systemPropertyAsInt("tests.multiplier", 1);

  public static final boolean TEST_ASSERTS_ENABLED = systemPropertyAsBoolean("tests.asserts", true);

  /** TODO: javadoc? */
  public static final String DEFAULT_LINE_DOCS_FILE = "europarl.lines.txt.gz";

  /** TODO: javadoc? */
  public static final String JENKINS_LARGE_LINE_DOCS_FILE = "enwiki.random.lines.txt";

  /** Gets the codec to run tests with. */
  public static final String TEST_CODEC = System.getProperty("tests.codec", "random");

  /** Gets the postingsFormat to run tests with. */
  public static final String TEST_POSTINGSFORMAT = System.getProperty("tests.postingsformat", "random");
  
  /** Gets the docValuesFormat to run tests with */
  public static final String TEST_DOCVALUESFORMAT = System.getProperty("tests.docvaluesformat", "random");

  /** Gets the directory to run tests with */
  public static final String TEST_DIRECTORY = System.getProperty("tests.directory", "random");

  /** the line file used by LineFileDocs */
  public static final String TEST_LINE_DOCS_FILE = System.getProperty("tests.linedocsfile", DEFAULT_LINE_DOCS_FILE);

  /** Whether or not {@link Nightly} tests should run. */
  public static final boolean TEST_NIGHTLY = systemPropertyAsBoolean(SYSPROP_NIGHTLY, Nightly.class.getAnnotation(TestGroup.class).enabled());

  /** Whether or not {@link Weekly} tests should run. */
  public static final boolean TEST_WEEKLY = systemPropertyAsBoolean(SYSPROP_WEEKLY, Weekly.class.getAnnotation(TestGroup.class).enabled());
  
  /** Whether or not {@link Monster} tests should run. */
  public static final boolean TEST_MONSTER = systemPropertyAsBoolean(SYSPROP_MONSTER, Monster.class.getAnnotation(TestGroup.class).enabled());

  /** Whether or not {@link AwaitsFix} tests should run. */
  public static final boolean TEST_AWAITSFIX = systemPropertyAsBoolean(SYSPROP_AWAITSFIX, AwaitsFix.class.getAnnotation(TestGroup.class).enabled());

  /** Whether or not {@link BadApple} tests should run. */
  public static final boolean TEST_BADAPPLES = systemPropertyAsBoolean(SYSPROP_BADAPPLES, BadApple.class.getAnnotation(TestGroup.class).enabled());

  /** Whether or not {@link Slow} tests should run. */
  public static final boolean TEST_SLOW = systemPropertyAsBoolean(SYSPROP_SLOW, Slow.class.getAnnotation(TestGroup.class).enabled());

  /** Throttling, see {@link MockDirectoryWrapper#setThrottling(Throttling)}. */
  public static final Throttling TEST_THROTTLING = TEST_NIGHTLY ? Throttling.SOMETIMES : Throttling.NEVER;

  /** Leave temporary files on disk, even on successful runs. */
  public static final boolean LEAVE_TEMPORARY;
  static {
    boolean defaultValue = false;
    for (String property : Arrays.asList(
        "tests.leaveTemporary" /* ANT tasks's (junit4) flag. */,
        "tests.leavetemporary" /* lowercase */,
        "tests.leavetmpdir" /* default */,
        "solr.test.leavetmpdir" /* Solr's legacy */)) {
      defaultValue |= systemPropertyAsBoolean(property, false);
    }
    LEAVE_TEMPORARY = defaultValue;
  }

  /** Returns true, if MMapDirectory supports unmapping on this platform (required for Windows), or if we are not on Windows. */
  public static boolean hasWorkingMMapOnWindows() {
    return !Constants.WINDOWS || MMapDirectory.UNMAP_SUPPORTED;
  }
  
  /** Assumes that the current MMapDirectory implementation supports unmapping, so the test will not fail on Windows.
   * @see #hasWorkingMMapOnWindows()
   * */
  public static void assumeWorkingMMapOnWindows() {
    assumeTrue(MMapDirectory.UNMAP_NOT_SUPPORTED_REASON, hasWorkingMMapOnWindows());
  }

  /** Filesystem-based {@link Directory} implementations. */
  private static final List<String> FS_DIRECTORIES = Arrays.asList(
    "SimpleFSDirectory",
    "NIOFSDirectory",
    // SimpleFSDirectory as replacement for MMapDirectory if unmapping is not supported on Windows (to make randomization stable):
    hasWorkingMMapOnWindows() ? "MMapDirectory" : "SimpleFSDirectory"
  );

  /** All {@link Directory} implementations. */
  private static final List<String> CORE_DIRECTORIES;
  static {
    CORE_DIRECTORIES = new ArrayList<>(FS_DIRECTORIES);
    CORE_DIRECTORIES.add("RAMDirectory");
    CORE_DIRECTORIES.add(ByteBuffersDirectory.class.getSimpleName());
  }
  
  /** A {@link org.apache.lucene.search.QueryCachingPolicy} that randomly caches. */
  public static final QueryCachingPolicy MAYBE_CACHE_POLICY = new QueryCachingPolicy() {

    @Override
    public void onUse(Query query) {}

    @Override
    public boolean shouldCache(Query query) throws IOException {
      return random().nextBoolean();
    }

  };
  
  // -----------------------------------------------------------------
  // Fields initialized in class or instance rules.
  // -----------------------------------------------------------------


  // -----------------------------------------------------------------
  // Class level (suite) rules.
  // -----------------------------------------------------------------
  
  /**
   * Stores the currently class under test.
   */
  private static final TestRuleStoreClassName classNameRule; 

  /**
   * Class environment setup rule.
   */
  static final TestRuleSetupAndRestoreClassEnv classEnvRule;

  /**
   * Suite failure marker (any error in the test or suite scope).
   */
  protected static TestRuleMarkFailure suiteFailureMarker;
  
  /**
   * Temporary files cleanup rule.
   */
  private static TestRuleTemporaryFilesCleanup tempFilesCleanupRule;

  /**
   * Ignore tests after hitting a designated number of initial failures. This
   * is truly a "static" global singleton since it needs to span the lifetime of all
   * test classes running inside this JVM (it cannot be part of a class rule).
   * 
   * <p>This poses some problems for the test framework's tests because these sometimes
   * trigger intentional failures which add up to the global count. This field contains
   * a (possibly) changing reference to {@link TestRuleIgnoreAfterMaxFailures} and we
   * dispatch to its current value from the {@link #classRules} chain using {@link TestRuleDelegate}.  
   */
  private static final AtomicReference<TestRuleIgnoreAfterMaxFailures> ignoreAfterMaxFailuresDelegate;
  private static final TestRule ignoreAfterMaxFailures;
  static {
    int maxFailures = systemPropertyAsInt(SYSPROP_MAXFAILURES, Integer.MAX_VALUE);
    boolean failFast = systemPropertyAsBoolean(SYSPROP_FAILFAST, false);

    if (failFast) {
      if (maxFailures == Integer.MAX_VALUE) {
        maxFailures = 1;
      } else {
        Logger.getLogger(LuceneTestCase.class.getSimpleName()).warning(
            "Property '" + SYSPROP_MAXFAILURES + "'=" + maxFailures + ", 'failfast' is" +
            " ignored.");
      }
    }

    ignoreAfterMaxFailuresDelegate = 
        new AtomicReference<>(
            new TestRuleIgnoreAfterMaxFailures(maxFailures));
    ignoreAfterMaxFailures = TestRuleDelegate.of(ignoreAfterMaxFailuresDelegate);
  }
  
  /**
   * Try to capture streams early so that other classes don't have a chance to steal references
   * to them (as is the case with ju.logging handlers).
   */
  static {
    TestRuleLimitSysouts.checkCaptureStreams();
    Logger.getGlobal().getHandlers();
  }

  /**
   * Temporarily substitute the global {@link TestRuleIgnoreAfterMaxFailures}. See
   * {@link #ignoreAfterMaxFailuresDelegate} for some explanation why this method 
   * is needed.
   */
  public static TestRuleIgnoreAfterMaxFailures replaceMaxFailureRule(TestRuleIgnoreAfterMaxFailures newValue) {
    return ignoreAfterMaxFailuresDelegate.getAndSet(newValue);
  }

  /**
   * Max 10mb of static data stored in a test suite class after the suite is complete.
   * Prevents static data structures leaking and causing OOMs in subsequent tests.
   */
  private final static long STATIC_LEAK_THRESHOLD = 10 * 1024 * 1024;

  /** By-name list of ignored types like loggers etc. */
  private final static Set<String> STATIC_LEAK_IGNORED_TYPES = Collections.unmodifiableSet(new HashSet<>(Arrays.asList(
      "org.slf4j.Logger",
      "org.apache.solr.SolrLogFormatter",
      "java.io.File", // Solr sometimes refers to this in a static way, but it has a "java.nio.fs.Path" inside 
      Path.class.getName(), // causes problems because interface is implemented by hidden classes
      Class.class.getName(),
      EnumSet.class.getName()
  )));

  /**
   * This controls how suite-level rules are nested. It is important that _all_ rules declared
   * in {@link LuceneTestCase} are executed in proper order if they depend on each 
   * other.
   */
  @ClassRule
  public static TestRule classRules;
  static {
    RuleChain r = RuleChain.outerRule(new TestRuleIgnoreTestSuites())
      .around(ignoreAfterMaxFailures)
      .around(suiteFailureMarker = new TestRuleMarkFailure())
      .around(new TestRuleAssertionsRequired())
      .around(new TestRuleLimitSysouts(suiteFailureMarker))
      .around(tempFilesCleanupRule = new TestRuleTemporaryFilesCleanup(suiteFailureMarker));
    // TODO LUCENE-7595: Java 9 does not allow to look into runtime classes, so we have to fix the RAM usage checker!
    if (!Constants.JRE_IS_MINIMUM_JAVA9) {
      r = r.around(new StaticFieldsInvariantRule(STATIC_LEAK_THRESHOLD, true) {
        @Override
        protected boolean accept(java.lang.reflect.Field field) {
          // Don't count known classes that consume memory once.
          if (STATIC_LEAK_IGNORED_TYPES.contains(field.getType().getName())) {
            return false;
          }
          // Don't count references from ourselves, we're top-level.
          if (field.getDeclaringClass() == LuceneTestCase.class) {
            return false;
          }
          return super.accept(field);
        }
      });
    }
    classRules = r.around(new NoClassHooksShadowingRule())
      .around(new NoInstanceHooksOverridesRule() {
        @Override
        protected boolean verify(Method key) {
          String name = key.getName();
          return !(name.equals("setUp") || name.equals("tearDown"));
        }
      })
      .around(classNameRule = new TestRuleStoreClassName())
      .around(new TestRuleRestoreSystemProperties(
          // Enlist all properties to which we have write access (security manager);
          // these should be restored to previous state, no matter what the outcome of the test.
  
          // We reset the default locale and timezone; these properties change as a side-effect
          "user.language",
          "user.timezone",
          
          // TODO: these should, ideally, be moved to Solr's base class.
          "solr.directoryFactory",
          "solr.solr.home",
          "solr.data.dir"
          ))
      .around(classEnvRule = new TestRuleSetupAndRestoreClassEnv());
  }

  // -----------------------------------------------------------------
  // Test level rules.
  // -----------------------------------------------------------------

  /** Enforces {@link #setUp()} and {@link #tearDown()} calls are chained. */
  private TestRuleSetupTeardownChained parentChainCallRule = new TestRuleSetupTeardownChained();

  /** Save test thread and name. */
  private TestRuleThreadAndTestName threadAndTestNameRule = new TestRuleThreadAndTestName();

  /** Taint suite result with individual test failures. */
  private TestRuleMarkFailure testFailureMarker = new TestRuleMarkFailure(suiteFailureMarker); 
  
  /**
   * This controls how individual test rules are nested. It is important that
   * _all_ rules declared in {@link LuceneTestCase} are executed in proper order
   * if they depend on each other.
   */
  @Rule
  public final TestRule ruleChain = RuleChain
    .outerRule(testFailureMarker)
    .around(ignoreAfterMaxFailures)
    .around(threadAndTestNameRule)
    .around(new TestRuleSetupAndRestoreInstanceEnv())
    .around(parentChainCallRule);

  private static final Map<String,FieldType> fieldToType = new HashMap<String,FieldType>();

  enum LiveIWCFlushMode {BY_RAM, BY_DOCS, EITHER};

  /** Set by TestRuleSetupAndRestoreClassEnv */
  static LiveIWCFlushMode liveIWCFlushMode;

  static void setLiveIWCFlushMode(LiveIWCFlushMode flushMode) {
    liveIWCFlushMode = flushMode;
  }

  // -----------------------------------------------------------------
  // Suite and test case setup/ cleanup.
  // -----------------------------------------------------------------

  /**
   * For subclasses to override. Overrides must call {@code super.setUp()}.
   */
  @Before
  public void setUp() throws Exception {
    parentChainCallRule.setupCalled = true;
  }

  /**
   * For subclasses to override. Overrides must call {@code super.tearDown()}.
   */
  @After
  public void tearDown() throws Exception {
    parentChainCallRule.teardownCalled = true;
    fieldToType.clear();

    // Test is supposed to call this itself, but we do this defensively in case it forgot:
    restoreIndexWriterMaxDocs();
  }

  /** Tells {@link IndexWriter} to enforce the specified limit as the maximum number of documents in one index; call
   *  {@link #restoreIndexWriterMaxDocs} once your test is done. */
  public void setIndexWriterMaxDocs(int limit) {
    IndexWriterMaxDocsChanger.setMaxDocs(limit);
  }

  /** Returns to the default {@link IndexWriter#MAX_DOCS} limit. */
  public void restoreIndexWriterMaxDocs() {
    IndexWriterMaxDocsChanger.restoreMaxDocs();
  }

  // -----------------------------------------------------------------
  // Test facilities and facades for subclasses. 
  // -----------------------------------------------------------------

  /**
   * Access to the current {@link RandomizedContext}'s Random instance. It is safe to use
   * this method from multiple threads, etc., but it should be called while within a runner's
   * scope (so no static initializers). The returned {@link Random} instance will be 
   * <b>different</b> when this method is called inside a {@link BeforeClass} hook (static 
   * suite scope) and within {@link Before}/ {@link After} hooks or test methods. 
   * 
   * <p>The returned instance must not be shared with other threads or cross a single scope's 
   * boundary. For example, a {@link Random} acquired within a test method shouldn't be reused
   * for another test case.
   * 
   * <p>There is an overhead connected with getting the {@link Random} for a particular context
   * and thread. It is better to cache the {@link Random} locally if tight loops with multiple
   * invocations are present or create a derivative local {@link Random} for millions of calls 
   * like this:
   * <pre>
   * Random random = new Random(random().nextLong());
   * // tight loop with many invocations. 
   * </pre>
   */
  public static Random random() {
    return RandomizedContext.current().getRandom();
  }

  /**
   * Registers a {@link Closeable} resource that should be closed after the test
   * completes.
   * 
   * @return <code>resource</code> (for call chaining).
   */
  public <T extends Closeable> T closeAfterTest(T resource) {
    return RandomizedContext.current().closeAtEnd(resource, LifecycleScope.TEST);
  }

  /**
   * Registers a {@link Closeable} resource that should be closed after the suite
   * completes.
   * 
   * @return <code>resource</code> (for call chaining).
   */
  public static <T extends Closeable> T closeAfterSuite(T resource) {
    return RandomizedContext.current().closeAtEnd(resource, LifecycleScope.SUITE);
  }

  /**
   * Return the current class being tested.
   */
  public static Class<?> getTestClass() {
    return classNameRule.getTestClass();
  }

  /**
   * Return the name of the currently executing test case.
   */
  public String getTestName() {
    return threadAndTestNameRule.testMethodName;
  }

  /**
   * Some tests expect the directory to contain a single segment, and want to 
   * do tests on that segment's reader. This is an utility method to help them.
   */
    /*
  public static SegmentReader getOnlySegmentReader(DirectoryReader reader) {
    List<LeafReaderContext> subReaders = reader.leaves();
    if (subReaders.size() != 1) {
      throw new IllegalArgumentException(reader + " has " + subReaders.size() + " segments instead of exactly one");
    }
    final LeafReader r = subReaders.get(0).reader();
    assertTrue("expected a SegmentReader but got " + r, r instanceof SegmentReader);
    return (SegmentReader) r;
  }
    */

  /**
   * Some tests expect the directory to contain a single segment, and want to 
   * do tests on that segment's reader. This is an utility method to help them.
   */
  public static LeafReader getOnlyLeafReader(IndexReader reader) {
    List<LeafReaderContext> subReaders = reader.leaves();
    if (subReaders.size() != 1) {
      throw new IllegalArgumentException(reader + " has " + subReaders.size() + " segments instead of exactly one");
    }
    return subReaders.get(0).reader();
  }

  /**
   * Returns true if and only if the calling thread is the primary thread 
   * executing the test case. 
   */
  protected boolean isTestThread() {
    assertNotNull("Test case thread not set?", threadAndTestNameRule.testCaseThread);
    return Thread.currentThread() == threadAndTestNameRule.testCaseThread;
  }

  /**
   * Returns a number of at least <code>i</code>
   * <p>
   * The actual number returned will be influenced by whether {@link #TEST_NIGHTLY}
   * is active and {@link #RANDOM_MULTIPLIER}, but also with some random fudge.
   */
  public static int atLeast(Random random, int i) {
    int min = (TEST_NIGHTLY ? 2*i : i) * RANDOM_MULTIPLIER;
    int max = min+(min/2);
    return TestUtil.nextInt(random, min, max);
  }
  
  public static int atLeast(int i) {
    return atLeast(random(), i);
  }
  
  /**
   * Returns true if something should happen rarely,
   * <p>
   * The actual number returned will be influenced by whether {@link #TEST_NIGHTLY}
   * is active and {@link #RANDOM_MULTIPLIER}.
   */
  public static boolean rarely(Random random) {
    int p = TEST_NIGHTLY ? 10 : 1;
    p += (p * Math.log(RANDOM_MULTIPLIER));
    int min = 100 - Math.min(p, 50); // never more than 50
    return random.nextInt(100) >= min;
  }
  
  public static boolean rarely() {
    return rarely(random());
  }
  
  public static boolean usually(Random random) {
    return !rarely(random);
  }
  
  public static boolean usually() {
    return usually(random());
  }

  public static void assumeTrue(String msg, boolean condition) {
    RandomizedTest.assumeTrue(msg, condition);
  }

  public static void assumeFalse(String msg, boolean condition) {
    RandomizedTest.assumeFalse(msg, condition);
  }

  public static void assumeNoException(String msg, Exception e) {
    RandomizedTest.assumeNoException(msg, e);
  }
  
  /**
   * Return <code>args</code> as a {@link Set} instance. The order of elements is not
   * preserved in iterators.
   */
  @SafeVarargs @SuppressWarnings("varargs")
  public static <T> Set<T> asSet(T... args) {
    return new HashSet<>(Arrays.asList(args));
  }

  /**
   * Convenience method for logging an iterator.
   *
   * @param label  String logged before/after the items in the iterator
   * @param iter   Each next() is toString()ed and logged on its own line. If iter is null this is logged differently then an empty iterator.
   * @param stream Stream to log messages to.
   */
  public static void dumpIterator(String label, Iterator<?> iter,
                                  PrintStream stream) {
    stream.println("*** BEGIN " + label + " ***");
    if (null == iter) {
      stream.println(" ... NULL ...");
    } else {
      while (iter.hasNext()) {
        stream.println(iter.next().toString());
      }
    }
    stream.println("*** END " + label + " ***");
  }

  /**
   * Convenience method for logging an array.  Wraps the array in an iterator and delegates
   *
   * @see #dumpIterator(String,Iterator,PrintStream)
   */
  public static void dumpArray(String label, Object[] objs,
                               PrintStream stream) {
    Iterator<?> iter = (null == objs) ? null : Arrays.asList(objs).iterator();
    dumpIterator(label, iter, stream);
  }

  /** create a new index writer config with random defaults */
  public static IndexWriterConfig newIndexWriterConfig() {
    return newIndexWriterConfig(new MockAnalyzer(random()));
  }

  /** create a new index writer config with random defaults */
  public static IndexWriterConfig newIndexWriterConfig(Analyzer a) {
    return newIndexWriterConfig(random(), a);
  }
  
  /** create a new index writer config with random defaults using the specified random */
  public static IndexWriterConfig newIndexWriterConfig(Random r, Analyzer a) {
    IndexWriterConfig c = new IndexWriterConfig(a);
    c.setSimilarity(classEnvRule.similarity);
    if (VERBOSE) {
      // Even though TestRuleSetupAndRestoreClassEnv calls
      // InfoStream.setDefault, we do it again here so that
      // the PrintStreamInfoStream.messageID increments so
      // that when there are separate instances of
      // IndexWriter created we see "IW 0", "IW 1", "IW 2",
      // ... instead of just always "IW 0":
      c.setInfoStream(new TestRuleSetupAndRestoreClassEnv.ThreadNameFixingPrintStreamInfoStream(System.out));
    }

    if (rarely(r)) {
      c.setMergeScheduler(new SerialMergeScheduler());
    } else if (rarely(r)) {
      ConcurrentMergeScheduler cms;
      if (r.nextBoolean()) {
        cms = new ConcurrentMergeScheduler();
      } else {
        cms = new ConcurrentMergeScheduler() {
            @Override
            protected synchronized boolean maybeStall(MergeSource mergeSource) {
              return true;
            }
          };
      }
      int maxThreadCount = TestUtil.nextInt(r, 1, 4);
      int maxMergeCount = TestUtil.nextInt(r, maxThreadCount, maxThreadCount + 4);
      cms.setMaxMergesAndThreads(maxMergeCount, maxThreadCount);
      if (random().nextBoolean()) {
        cms.disableAutoIOThrottle();
        assertFalse(cms.getAutoIOThrottle());
      }
      cms.setForceMergeMBPerSec(10 + 10*random().nextDouble());
      c.setMergeScheduler(cms);
    } else {
      // Always use consistent settings, else CMS's dynamic (SSD or not)
      // defaults can change, hurting reproducibility:
      ConcurrentMergeScheduler cms = new ConcurrentMergeScheduler();

      // Only 1 thread can run at once (should maybe help reproducibility),
      // with up to 3 pending merges before segment-producing threads are
      // stalled:
      cms.setMaxMergesAndThreads(3, 1);
      c.setMergeScheduler(cms);
    }

    if (r.nextBoolean()) {
      if (rarely(r)) {
        // crazy value
        c.setMaxBufferedDocs(TestUtil.nextInt(r, 2, 15));
      } else {
        // reasonable value
        c.setMaxBufferedDocs(TestUtil.nextInt(r, 16, 1000));
      }
    }

    c.setMergePolicy(newMergePolicy(r));

    avoidPathologicalMerging(c);

    if (rarely(r)) {
      c.setMergedSegmentWarmer(new SimpleMergedSegmentWarmer(c.getInfoStream()));
    }
    c.setUseCompoundFile(r.nextBoolean());
    c.setReaderPooling(r.nextBoolean());
    if (rarely(r)) {
      c.setCheckPendingFlushUpdate(false);
    }
    c.setMaxFullFlushMergeWaitMillis(rarely() ?  atLeast(r, 1000) : atLeast(r, 200));
    return c;
  }

  private static void avoidPathologicalMerging(IndexWriterConfig iwc) {
    // Don't allow "tiny" flushed segments with "big" merge
    // floor: this leads to pathological O(N^2) merge costs:
    long estFlushSizeBytes = Long.MAX_VALUE;
    if (iwc.getMaxBufferedDocs() != IndexWriterConfig.DISABLE_AUTO_FLUSH) {
      // Gross estimation of 1 KB segment bytes for each doc indexed:
      estFlushSizeBytes = Math.min(estFlushSizeBytes, iwc.getMaxBufferedDocs() * 1024);
    }
    if (iwc.getRAMBufferSizeMB() != IndexWriterConfig.DISABLE_AUTO_FLUSH) {
      estFlushSizeBytes = Math.min(estFlushSizeBytes, (long) (iwc.getRAMBufferSizeMB() * 1024 * 1024));
    }
    assert estFlushSizeBytes > 0;

    MergePolicy mp = iwc.getMergePolicy();
    if (mp instanceof TieredMergePolicy) {
      TieredMergePolicy tmp = (TieredMergePolicy) mp;
      long floorSegBytes = (long) (tmp.getFloorSegmentMB() * 1024 * 1024);
      if (floorSegBytes / estFlushSizeBytes > 10) {
        double newValue = estFlushSizeBytes * 10.0 / 1024 / 1024;
        if (VERBOSE) {
          System.out.println("NOTE: LuceneTestCase: changing TieredMergePolicy.floorSegmentMB from " + tmp.getFloorSegmentMB() + " to " + newValue + " to avoid pathological merging");
        }
        tmp.setFloorSegmentMB(newValue);
      }
    } else if (mp instanceof LogByteSizeMergePolicy) {
      LogByteSizeMergePolicy lmp = (LogByteSizeMergePolicy) mp;
      if ((lmp.getMinMergeMB()*1024*1024) / estFlushSizeBytes > 10) {
        double newValue = estFlushSizeBytes * 10.0 / 1024 / 1024;
        if (VERBOSE) {
          System.out.println("NOTE: LuceneTestCase: changing LogByteSizeMergePolicy.minMergeMB from " + lmp.getMinMergeMB() + " to " + newValue + " to avoid pathological merging");
        }
        lmp.setMinMergeMB(newValue);
      }
    } else if (mp instanceof LogDocMergePolicy) {
      LogDocMergePolicy lmp = (LogDocMergePolicy) mp;
      assert estFlushSizeBytes / 1024 < Integer.MAX_VALUE/10;
      int estFlushDocs = Math.max(1, (int) (estFlushSizeBytes / 1024));
      if (lmp.getMinMergeDocs() / estFlushDocs > 10) {
        int newValue = estFlushDocs * 10;
        if (VERBOSE) {
          System.out.println("NOTE: LuceneTestCase: changing LogDocMergePolicy.minMergeDocs from " + lmp.getMinMergeDocs() + " to " + newValue + " to avoid pathological merging");
        }
        lmp.setMinMergeDocs(newValue);
      }
    }
  }

  public static MergePolicy newMergePolicy(Random r) {
    return newMergePolicy(r, true);
  }

  public static MergePolicy newMergePolicy(Random r, boolean includeMockMP) {
    if (includeMockMP && rarely(r)) {
      return new MockRandomMergePolicy(r);
    } else if (r.nextBoolean()) {
      return newTieredMergePolicy(r);
    } else if (rarely(r) ) { 
      return newAlcoholicMergePolicy(r, classEnvRule.timeZone);
    }
    return newLogMergePolicy(r);
  }

  public static MergePolicy newMergePolicy() {
    return newMergePolicy(random());
  }

  public static LogMergePolicy newLogMergePolicy() {
    return newLogMergePolicy(random());
  }

  public static TieredMergePolicy newTieredMergePolicy() {
    return newTieredMergePolicy(random());
  }

  public static AlcoholicMergePolicy newAlcoholicMergePolicy() {
    return newAlcoholicMergePolicy(random(), classEnvRule.timeZone);
  }
  
  public static AlcoholicMergePolicy newAlcoholicMergePolicy(Random r, TimeZone tz) {
    return new AlcoholicMergePolicy(tz, new Random(r.nextLong()));
  }

  public static LogMergePolicy newLogMergePolicy(Random r) {
    LogMergePolicy logmp = r.nextBoolean() ? new LogDocMergePolicy() : new LogByteSizeMergePolicy();
    logmp.setCalibrateSizeByDeletes(r.nextBoolean());
    if (rarely(r)) {
      logmp.setMergeFactor(TestUtil.nextInt(r, 2, 9));
    } else {
      logmp.setMergeFactor(TestUtil.nextInt(r, 10, 50));
    }
    configureRandom(r, logmp);
    return logmp;
  }
  
  private static void configureRandom(Random r, MergePolicy mergePolicy) {
    if (r.nextBoolean()) {
      mergePolicy.setNoCFSRatio(0.1 + r.nextDouble()*0.8);
    } else {
      mergePolicy.setNoCFSRatio(r.nextBoolean() ? 1.0 : 0.0);
    }
    
    if (rarely(r)) {
      mergePolicy.setMaxCFSSegmentSizeMB(0.2 + r.nextDouble() * 2.0);
    } else {
      mergePolicy.setMaxCFSSegmentSizeMB(Double.POSITIVE_INFINITY);
    }
  }

  public static TieredMergePolicy newTieredMergePolicy(Random r) {
    TieredMergePolicy tmp = new TieredMergePolicy();
    if (rarely(r)) {
      tmp.setMaxMergeAtOnce(TestUtil.nextInt(r, 2, 9));
      tmp.setMaxMergeAtOnceExplicit(TestUtil.nextInt(r, 2, 9));
    } else {
      tmp.setMaxMergeAtOnce(TestUtil.nextInt(r, 10, 50));
      tmp.setMaxMergeAtOnceExplicit(TestUtil.nextInt(r, 10, 50));
    }
    if (rarely(r)) {
      tmp.setMaxMergedSegmentMB(0.2 + r.nextDouble() * 2.0);
    } else {
      tmp.setMaxMergedSegmentMB(10 + r.nextDouble() * 100);
    }
    tmp.setFloorSegmentMB(0.2 + r.nextDouble() * 2.0);
    tmp.setForceMergeDeletesPctAllowed(0.0 + r.nextDouble() * 30.0);
    if (rarely(r)) {
      tmp.setSegmentsPerTier(TestUtil.nextInt(r, 2, 20));
    } else {
      tmp.setSegmentsPerTier(TestUtil.nextInt(r, 10, 50));
    }
    configureRandom(r, tmp);
    tmp.setDeletesPctAllowed(20 + random().nextDouble() * 30);
    return tmp;
  }

  public static MergePolicy newLogMergePolicy(boolean useCFS) {
    MergePolicy logmp = newLogMergePolicy();
    logmp.setNoCFSRatio(useCFS ? 1.0 : 0.0);
    return logmp;
  }

  public static MergePolicy newLogMergePolicy(boolean useCFS, int mergeFactor) {
    LogMergePolicy logmp = newLogMergePolicy();
    logmp.setNoCFSRatio(useCFS ? 1.0 : 0.0);
    logmp.setMergeFactor(mergeFactor);
    return logmp;
  }

  public static MergePolicy newLogMergePolicy(int mergeFactor) {
    LogMergePolicy logmp = newLogMergePolicy();
    logmp.setMergeFactor(mergeFactor);
    return logmp;
  }
  
  // if you want it in LiveIndexWriterConfig: it must and will be tested here.
  public static void maybeChangeLiveIndexWriterConfig(Random r, LiveIndexWriterConfig c) {
    boolean didChange = false;

    String previous = c.toString();
    
    if (rarely(r)) {
      // change flush parameters:
      // this is complicated because the api requires you "invoke setters in a magical order!"
      // LUCENE-5661: workaround for race conditions in the API
      synchronized (c) {
        boolean flushByRAM;
        switch (liveIWCFlushMode) {
        case BY_RAM:
          flushByRAM = true;
          break;
        case BY_DOCS:
          flushByRAM = false;
          break;
        case EITHER:
          flushByRAM = r.nextBoolean();
          break;
        default:
          throw new AssertionError();
        }
        if (flushByRAM) { 
          c.setRAMBufferSizeMB(TestUtil.nextInt(r, 1, 10));
          c.setMaxBufferedDocs(IndexWriterConfig.DISABLE_AUTO_FLUSH);
        } else {
          if (rarely(r)) {
            // crazy value
            c.setMaxBufferedDocs(TestUtil.nextInt(r, 2, 15));
          } else {
            // reasonable value
            c.setMaxBufferedDocs(TestUtil.nextInt(r, 16, 1000));
          }
          c.setRAMBufferSizeMB(IndexWriterConfig.DISABLE_AUTO_FLUSH);
        }
      }
      didChange = true;
    }
    
    if (rarely(r)) {
      IndexWriter.IndexReaderWarmer curWarmer = c.getMergedSegmentWarmer();
      if (curWarmer == null || curWarmer instanceof SimpleMergedSegmentWarmer) {
        // change warmer parameters
        if (r.nextBoolean()) {
          c.setMergedSegmentWarmer(new SimpleMergedSegmentWarmer(c.getInfoStream()));
        } else {
          c.setMergedSegmentWarmer(null);
        }
      }
      didChange = true;
    }
    
    if (rarely(r)) {
      // change CFS flush parameters
      c.setUseCompoundFile(r.nextBoolean());
      didChange = true;
    }
    
    if (rarely(r)) {
      // change CMS merge parameters
      MergeScheduler ms = c.getMergeScheduler();
      if (ms instanceof ConcurrentMergeScheduler) {
        ConcurrentMergeScheduler cms = (ConcurrentMergeScheduler) ms;
        int maxThreadCount = TestUtil.nextInt(r, 1, 4);
        int maxMergeCount = TestUtil.nextInt(r, maxThreadCount, maxThreadCount + 4);
        boolean enableAutoIOThrottle = random().nextBoolean();
        if (enableAutoIOThrottle) {
          cms.enableAutoIOThrottle();
        } else {
          cms.disableAutoIOThrottle();
        }
        cms.setMaxMergesAndThreads(maxMergeCount, maxThreadCount);
        didChange = true;
      }
    }
    
    if (rarely(r)) {
      MergePolicy mp = c.getMergePolicy();
      configureRandom(r, mp);
      if (mp instanceof LogMergePolicy) {
        LogMergePolicy logmp = (LogMergePolicy) mp;
        logmp.setCalibrateSizeByDeletes(r.nextBoolean());
        if (rarely(r)) {
          logmp.setMergeFactor(TestUtil.nextInt(r, 2, 9));
        } else {
          logmp.setMergeFactor(TestUtil.nextInt(r, 10, 50));
        }
      } else if (mp instanceof TieredMergePolicy) {
        TieredMergePolicy tmp = (TieredMergePolicy) mp;
        if (rarely(r)) {
          tmp.setMaxMergeAtOnce(TestUtil.nextInt(r, 2, 9));
          tmp.setMaxMergeAtOnceExplicit(TestUtil.nextInt(r, 2, 9));
        } else {
          tmp.setMaxMergeAtOnce(TestUtil.nextInt(r, 10, 50));
          tmp.setMaxMergeAtOnceExplicit(TestUtil.nextInt(r, 10, 50));
        }
        if (rarely(r)) {
          tmp.setMaxMergedSegmentMB(0.2 + r.nextDouble() * 2.0);
        } else {
          tmp.setMaxMergedSegmentMB(r.nextDouble() * 100);
        }
        tmp.setFloorSegmentMB(0.2 + r.nextDouble() * 2.0);
        tmp.setForceMergeDeletesPctAllowed(0.0 + r.nextDouble() * 30.0);
        if (rarely(r)) {
          tmp.setSegmentsPerTier(TestUtil.nextInt(r, 2, 20));
        } else {
          tmp.setSegmentsPerTier(TestUtil.nextInt(r, 10, 50));
        }
        configureRandom(r, tmp);
        tmp.setDeletesPctAllowed(20 + random().nextDouble() * 30);
      }
      didChange = true;
    }
    if (VERBOSE && didChange) {
      String current = c.toString();
      String previousLines[] = previous.split("\n");
      String currentLines[] = current.split("\n");
      StringBuilder diff = new StringBuilder();

      // this should always be the case, diff each line
      if (previousLines.length == currentLines.length) {
        for (int i = 0; i < previousLines.length; i++) {
          if (!previousLines[i].equals(currentLines[i])) {
            diff.append("- ").append(previousLines[i]).append("\n");
            diff.append("+ ").append(currentLines[i]).append("\n");
          }
        }
      } else {
        // but just in case of something ridiculous...
        diff.append(current.toString());
      }
      
      // its possible to be empty, if we "change" a value to what it had before.
      if (diff.length() > 0) {
        System.out.println("NOTE: LuceneTestCase: randomly changed IWC's live settings:");
        System.out.println(diff);
      }
    }
  }

  /**
   * Returns a new Directory instance. Use this when the test does not
   * care about the specific Directory implementation (most tests).
   * <p>
   * The Directory is wrapped with {@link BaseDirectoryWrapper}.
   * this means usually it will be picky, such as ensuring that you
   * properly close it and all open files in your test. It will emulate
   * some features of Windows, such as not allowing open files to be
   * overwritten.
   */
  public static BaseDirectoryWrapper newDirectory() {
    return newDirectory(random());
  }

  /** Like {@link #newDirectory} except randomly the {@link VirusCheckingFS} may be installed */
  public static BaseDirectoryWrapper newMaybeVirusCheckingDirectory() {
    if (random().nextInt(5) == 4) {
      Path path = addVirusChecker(createTempDir());
      return newFSDirectory(path);
    } else {
      return newDirectory(random());
    }
  }
  
  /**
   * Returns a new Directory instance, using the specified random.
   * See {@link #newDirectory()} for more information.
   */
  public static BaseDirectoryWrapper newDirectory(Random r) {
    return wrapDirectory(r, newDirectoryImpl(r, TEST_DIRECTORY), rarely(r), false);
  }

  /**
   * Returns a new Directory instance, using the specified random.
   * See {@link #newDirectory()} for more information.
   */
  public static BaseDirectoryWrapper newDirectory(Random r, LockFactory lf) {
    return wrapDirectory(r, newDirectoryImpl(r, TEST_DIRECTORY, lf), rarely(r), false);
  }

  public static MockDirectoryWrapper newMockDirectory() {
    return newMockDirectory(random());
  }

  public static MockDirectoryWrapper newMockDirectory(Random r) {
    return (MockDirectoryWrapper) wrapDirectory(r, newDirectoryImpl(r, TEST_DIRECTORY), false, false);
  }

  public static MockDirectoryWrapper newMockDirectory(Random r, LockFactory lf) {
    return (MockDirectoryWrapper) wrapDirectory(r, newDirectoryImpl(r, TEST_DIRECTORY, lf), false, false);
  }

  public static MockDirectoryWrapper newMockFSDirectory(Path f) {
    return (MockDirectoryWrapper) newFSDirectory(f, FSLockFactory.getDefault(), false);
  }

  public static MockDirectoryWrapper newMockFSDirectory(Path f, LockFactory lf) {
    return (MockDirectoryWrapper) newFSDirectory(f, lf, false);
  }

  public static Path addVirusChecker(Path path) {
    if (TestUtil.hasVirusChecker(path) == false) {
      VirusCheckingFS fs = new VirusCheckingFS(path.getFileSystem(), random().nextLong());
      FileSystem filesystem = fs.getFileSystem(URI.create("file:///"));
      path = new FilterPath(path, filesystem);
    }
    return path;
  }

  /**
   * Returns a new Directory instance, with contents copied from the
   * provided directory. See {@link #newDirectory()} for more
   * information.
   */
  public static BaseDirectoryWrapper newDirectory(Directory d) throws IOException {
    return newDirectory(random(), d);
  }

  /** Returns a new FSDirectory instance over the given file, which must be a folder. */
  public static BaseDirectoryWrapper newFSDirectory(Path f) {
    return newFSDirectory(f, FSLockFactory.getDefault());
  }

  /** Like {@link #newFSDirectory(Path)}, but randomly insert {@link VirusCheckingFS} */
  public static BaseDirectoryWrapper newMaybeVirusCheckingFSDirectory(Path f) {
    if (random().nextInt(5) == 4) {
      f = addVirusChecker(f);
    }
    return newFSDirectory(f, FSLockFactory.getDefault());
  }

  /** Returns a new FSDirectory instance over the given file, which must be a folder. */
  public static BaseDirectoryWrapper newFSDirectory(Path f, LockFactory lf) {
    return newFSDirectory(f, lf, rarely());
  }

  private static BaseDirectoryWrapper newFSDirectory(Path f, LockFactory lf, boolean bare) {
    String fsdirClass = TEST_DIRECTORY;
    if (fsdirClass.equals("random")) {
      fsdirClass = RandomPicks.randomFrom(random(), FS_DIRECTORIES); 
    }

    Class<? extends FSDirectory> clazz;
    try {
      try {
        clazz = CommandLineUtil.loadFSDirectoryClass(fsdirClass);
      } catch (ClassCastException e) {
        // TEST_DIRECTORY is not a sub-class of FSDirectory, so draw one at random
        fsdirClass = RandomPicks.randomFrom(random(), FS_DIRECTORIES);
        clazz = CommandLineUtil.loadFSDirectoryClass(fsdirClass);
      }

      Directory fsdir = newFSDirectoryImpl(clazz, f, lf);
      BaseDirectoryWrapper wrapped = wrapDirectory(random(), fsdir, bare, true);
      return wrapped;
    } catch (Exception e) {
      Rethrow.rethrow(e);
      throw null; // dummy to prevent compiler failure
    }
  }

  private static Directory newFileSwitchDirectory(Random random, Directory dir1, Directory dir2) {
    List<String> fileExtensions =
        Arrays.asList("fdt", "fdx", "tim", "tip", "si", "fnm", "pos", "dii", "dim", "nvm", "nvd", "dvm", "dvd");
    Collections.shuffle(fileExtensions, random);
    fileExtensions = fileExtensions.subList(0, 1 + random.nextInt(fileExtensions.size()));
    return new FileSwitchDirectory(new HashSet<>(fileExtensions), dir1, dir2, true);
  }

  /**
   * Returns a new Directory instance, using the specified random
   * with contents copied from the provided directory. See 
   * {@link #newDirectory()} for more information.
   */
  public static BaseDirectoryWrapper newDirectory(Random r, Directory d) throws IOException {
    Directory impl = newDirectoryImpl(r, TEST_DIRECTORY);
    for (String file : d.listAll()) {
      if (file.startsWith(IndexFileNames.SEGMENTS) || IndexFileNames.CODEC_FILE_PATTERN.matcher(file).matches()) {
        impl.copyFrom(d, file, file, newIOContext(r));
      }
    }
    return wrapDirectory(r, impl, rarely(r), false);
  }
  
  private static BaseDirectoryWrapper wrapDirectory(Random random, Directory directory, boolean bare, boolean filesystem) {
    // IOContext randomization might make NRTCachingDirectory make bad decisions, so avoid
    // using it if the user requested a filesystem directory.
    if (rarely(random) && !bare && filesystem == false) {
      directory = new NRTCachingDirectory(directory, random.nextDouble(), random.nextDouble());
    }

    if (bare) {
      BaseDirectoryWrapper base = new RawDirectoryWrapper(directory);
      closeAfterSuite(new CloseableDirectory(base, suiteFailureMarker));
      return base;
    } else {
      MockDirectoryWrapper mock = new MockDirectoryWrapper(random, directory);
      
      mock.setThrottling(TEST_THROTTLING);
      closeAfterSuite(new CloseableDirectory(mock, suiteFailureMarker));
      return mock;
    }
  }
  
  public static Field newStringField(String name, String value, Store stored) {
    return newField(random(), name, value, stored == Store.YES ? StringField.TYPE_STORED : StringField.TYPE_NOT_STORED);
  }

  public static Field newStringField(String name, BytesRef value, Store stored) {
    return newField(random(), name, value, stored == Store.YES ? StringField.TYPE_STORED : StringField.TYPE_NOT_STORED);
  }

  public static Field newTextField(String name, String value, Store stored) {
    return newField(random(), name, value, stored == Store.YES ? TextField.TYPE_STORED : TextField.TYPE_NOT_STORED);
  }
  
  public static Field newStringField(Random random, String name, String value, Store stored) {
    return newField(random, name, value, stored == Store.YES ? StringField.TYPE_STORED : StringField.TYPE_NOT_STORED);
  }

  public static Field newStringField(Random random, String name, BytesRef value, Store stored) {
    return newField(random, name, value, stored == Store.YES ? StringField.TYPE_STORED : StringField.TYPE_NOT_STORED);
  }
  
  public static Field newTextField(Random random, String name, String value, Store stored) {
    return newField(random, name, value, stored == Store.YES ? TextField.TYPE_STORED : TextField.TYPE_NOT_STORED);
  }
  
  public static Field newField(String name, String value, FieldType type) {
    return newField(random(), name, value, type);
  }

  /** Returns a FieldType derived from newType but whose
   *  term vector options match the old type */
  private static FieldType mergeTermVectorOptions(FieldType newType, FieldType oldType) {
    if (newType.indexOptions() != IndexOptions.NONE && oldType.storeTermVectors() == true && newType.storeTermVectors() == false) {
      newType = new FieldType(newType);
      newType.setStoreTermVectors(oldType.storeTermVectors());
      newType.setStoreTermVectorPositions(oldType.storeTermVectorPositions());
      newType.setStoreTermVectorOffsets(oldType.storeTermVectorOffsets());
      newType.setStoreTermVectorPayloads(oldType.storeTermVectorPayloads());
      newType.freeze();
    }

    return newType;
  }

  // TODO: if we can pull out the "make term vector options
  // consistent across all instances of the same field name"
  // write-once schema sort of helper class then we can
  // remove the sync here.  We can also fold the random
  // "enable norms" (now commented out, below) into that:
  public synchronized static Field newField(Random random, String name, Object value, FieldType type) {

    // Defeat any consumers that illegally rely on intern'd
    // strings (we removed this from Lucene a while back):
    name = new String(name);

    FieldType prevType = fieldToType.get(name);

    if (usually(random) || type.indexOptions() == IndexOptions.NONE || prevType != null) {
      // most of the time, don't modify the params
      if (prevType == null) {
        fieldToType.put(name, new FieldType(type));
      } else {
        type = mergeTermVectorOptions(type, prevType);
      }

      return createField(name, value, type);
    }

    // TODO: once all core & test codecs can index
    // offsets, sometimes randomly turn on offsets if we are
    // already indexing positions...

    FieldType newType = new FieldType(type);
    if (!newType.stored() && random.nextBoolean()) {
      newType.setStored(true); // randomly store it
    }

    // Randomly turn on term vector options, but always do
    // so consistently for the same field name:
    if (!newType.storeTermVectors() && random.nextBoolean()) {
      newType.setStoreTermVectors(true);
      if (!newType.storeTermVectorPositions()) {
        newType.setStoreTermVectorPositions(random.nextBoolean());
        
        if (newType.storeTermVectorPositions()) {
          if (!newType.storeTermVectorPayloads()) {
            newType.setStoreTermVectorPayloads(random.nextBoolean());
          }
        }
      }
      
      if (!newType.storeTermVectorOffsets()) {
        newType.setStoreTermVectorOffsets(random.nextBoolean());
      }

      if (VERBOSE) {
        System.out.println("NOTE: LuceneTestCase: upgrade name=" + name + " type=" + newType);
      }
    }
    newType.freeze();
    fieldToType.put(name, newType);

    // TODO: we need to do this, but smarter, ie, most of
    // the time we set the same value for a given field but
    // sometimes (rarely) we change it up:
    /*
    if (newType.omitNorms()) {
      newType.setOmitNorms(random.nextBoolean());
    }
    */
    
    return createField(name, value, newType);
  }

  private static Field createField(String name, Object value, FieldType fieldType) {
    if (value instanceof String) {
      return new Field(name, (String) value, fieldType);
    } else if (value instanceof BytesRef) {
      return new Field(name, (BytesRef) value, fieldType);
    } else {
      throw new IllegalArgumentException("value must be String or BytesRef");
    }
  }
  
  private static final String[] availableLanguageTags = Arrays.stream(Locale.getAvailableLocales())
      .map(Locale::toLanguageTag)
      .sorted()
      .distinct()
      .toArray(String[]::new);

  /** 
   * Return a random Locale from the available locales on the system.
   * @see <a href="http://issues.apache.org/jira/browse/LUCENE-4020">LUCENE-4020</a>
   */
  public static Locale randomLocale(Random random) {
    return localeForLanguageTag(availableLanguageTags[random.nextInt(availableLanguageTags.length)]);
  }

  /** 
   * Return a random TimeZone from the available timezones on the system
   * @see <a href="http://issues.apache.org/jira/browse/LUCENE-4020">LUCENE-4020</a>
   */
  public static TimeZone randomTimeZone(Random random) {
    String tzIds[] = TimeZone.getAvailableIDs();
    return TimeZone.getTimeZone(tzIds[random.nextInt(tzIds.length)]);
  }

  /** return a Locale object equivalent to its programmatic name */
  public static Locale localeForLanguageTag(String languageTag) {
    return new Locale.Builder().setLanguageTag(languageTag).build();
  }

  private static Directory newFSDirectoryImpl(Class<? extends FSDirectory> clazz, Path path, LockFactory lf) throws IOException {
    FSDirectory d = null;
    try {
      d = CommandLineUtil.newFSDirectory(clazz, path, lf);
    } catch (ReflectiveOperationException e) {
      Rethrow.rethrow(e);
    }
    return d;
  }

  static Directory newDirectoryImpl(Random random, String clazzName) {
    return newDirectoryImpl(random, clazzName, FSLockFactory.getDefault());
  }
  
  static Directory newDirectoryImpl(Random random, String clazzName, LockFactory lf) {
    if (clazzName.equals("random")) {
      if (rarely(random)) {
        clazzName = RandomPicks.randomFrom(random, CORE_DIRECTORIES);
      } else if (rarely(random)) {
        String clazzName1 = rarely(random)
            ? RandomPicks.randomFrom(random, CORE_DIRECTORIES)
            : ByteBuffersDirectory.class.getName();
        String clazzName2 = rarely(random)
            ? RandomPicks.randomFrom(random, CORE_DIRECTORIES)
            : ByteBuffersDirectory.class.getName();
        return newFileSwitchDirectory(random,
            newDirectoryImpl(random, clazzName1, lf),
            newDirectoryImpl(random, clazzName2, lf));
      } else {
        clazzName = "RAMDirectory";
      }
    }

    try {
      final Class<? extends Directory> clazz = CommandLineUtil.loadDirectoryClass(clazzName);
      // If it is a FSDirectory type, try its ctor(Path)
      if (FSDirectory.class.isAssignableFrom(clazz)) {
        final Path dir = createTempDir("index-" + clazzName);
        return newFSDirectoryImpl(clazz.asSubclass(FSDirectory.class), dir, lf);
      }

      // See if it has a Path/LockFactory ctor even though it's not an
      // FSDir subclass:
      try {
        Constructor<? extends Directory> pathCtor = clazz.getConstructor(Path.class, LockFactory.class);
        final Path dir = createTempDir("index");
        return pathCtor.newInstance(dir, lf);
      } catch (NoSuchMethodException nsme) {
        // Ignore
      }
      
      // the remaining dirs are no longer filesystem based, so we must check that the passedLockFactory is not file based:
      if (!(lf instanceof FSLockFactory)) {
        // try ctor with only LockFactory (e.g. RAMDirectory)
        try {
          return clazz.getConstructor(LockFactory.class).newInstance(lf);
        } catch (NoSuchMethodException nsme) {
          // Ignore
        }
      }

      // try empty ctor
      return clazz.newInstance();
    } catch (Exception e) {
      Rethrow.rethrow(e);
      throw null; // dummy to prevent compiler failure
    }
  }

  public static IndexReader wrapReader(IndexReader r) throws IOException {
    Random random = random();
      
    for (int i = 0, c = random.nextInt(6)+1; i < c; i++) {
      switch(random.nextInt(5)) {
      case 0:
        // will create no FC insanity in atomic case, as ParallelLeafReader has own cache key:
        if (VERBOSE) {
          System.out.println("NOTE: LuceneTestCase.wrapReader: wrapping previous reader=" + r + " with ParallelLeaf/CompositeReader");
        }
        r = (r instanceof LeafReader) ?
          new ParallelLeafReader((LeafReader) r) :
        new ParallelCompositeReader((CompositeReader) r);
        break;
      case 1:
        if (r instanceof LeafReader) {
          final LeafReader ar = (LeafReader) r;
          final List<String> allFields = new ArrayList<>();
          for (FieldInfo fi : ar.getFieldInfos()) {
            allFields.add(fi.name);
          }
          Collections.shuffle(allFields, random);
          final int end = allFields.isEmpty() ? 0 : random.nextInt(allFields.size());
          final Set<String> fields = new HashSet<>(allFields.subList(0, end));
          // will create no FC insanity as ParallelLeafReader has own cache key:
          if (VERBOSE) {
            System.out.println("NOTE: LuceneTestCase.wrapReader: wrapping previous reader=" + r + " with ParallelLeafReader");
          }
          r = new ParallelLeafReader(
                                     new FieldFilterLeafReader(ar, fields, false),
                                     new FieldFilterLeafReader(ar, fields, true)
                                     );
        }
        break;
      case 2:
        // Häckidy-Hick-Hack: a standard Reader will cause FC insanity, so we use
        // QueryUtils' reader with a fake cache key, so insanity checker cannot walk
        // along our reader:
        if (VERBOSE) {
          System.out.println("NOTE: LuceneTestCase.wrapReader: wrapping previous reader=" + r + " with AssertingLeaf/DirectoryReader");
        }
        if (r instanceof LeafReader) {
          r = new AssertingLeafReader((LeafReader)r);
        } else if (r instanceof DirectoryReader) {
          r = new AssertingDirectoryReader((DirectoryReader)r);
        }
        break;
      case 3:
        if (VERBOSE) {
          System.out.println("NOTE: LuceneTestCase.wrapReader: wrapping previous reader=" + r + " with MismatchedLeaf/DirectoryReader");
        }
        if (r instanceof LeafReader) {
          r = new MismatchedLeafReader((LeafReader)r, random);
        } else if (r instanceof DirectoryReader) {
          r = new MismatchedDirectoryReader((DirectoryReader)r, random);
        }
        break;
      case 4:
        if (VERBOSE) {
          System.out.println("NOTE: LuceneTestCase.wrapReader: wrapping previous reader=" + r + " with MergingCodecReader");
        }
        if (r instanceof CodecReader) {
          r = new MergingCodecReader((CodecReader) r);
        } else if (r instanceof DirectoryReader) {
          boolean allLeavesAreCodecReaders = true;
          for (LeafReaderContext ctx : r.leaves()) {
            if (ctx.reader() instanceof CodecReader == false) {
              allLeavesAreCodecReaders = false;
              break;
            }
          }
          if (allLeavesAreCodecReaders) {
            r = new MergingDirectoryReaderWrapper((DirectoryReader) r);
          }
        }
        break;
      default:
        fail("should not get here");
      }
    }

    if (VERBOSE) {
      System.out.println("wrapReader wrapped: " +r);
    }

    return r;
  }
  
  /**
   * Sometimes wrap the IndexReader as slow, parallel or filter reader (or
   * combinations of that)
   */
  public static IndexReader maybeWrapReader(IndexReader r) throws IOException {
    if (rarely()) {
      r = wrapReader(r);
    }
    return r;
  }

  /** TODO: javadoc */
  public static IOContext newIOContext(Random random) {
    return newIOContext(random, IOContext.DEFAULT);
  }

  /** TODO: javadoc */
  public static IOContext newIOContext(Random random, IOContext oldContext) {
    final int randomNumDocs = random.nextInt(4192);
    final int size = random.nextInt(512) * randomNumDocs;
    if (oldContext.flushInfo != null) {
      // Always return at least the estimatedSegmentSize of
      // the incoming IOContext:
      return new IOContext(new FlushInfo(randomNumDocs, Math.max(oldContext.flushInfo.estimatedSegmentSize, size)));
    } else if (oldContext.mergeInfo != null) {
      // Always return at least the estimatedMergeBytes of
      // the incoming IOContext:
      return new IOContext(new MergeInfo(randomNumDocs, Math.max(oldContext.mergeInfo.estimatedMergeBytes, size), random.nextBoolean(), TestUtil.nextInt(random, 1, 100)));
    } else {
      // Make a totally random IOContext:
      final IOContext context;
      switch (random.nextInt(5)) {
      case 0:
        context = IOContext.DEFAULT;
        break;
      case 1:
        context = IOContext.READ;
        break;
      case 2:
        context = IOContext.READONCE;
        break;
      case 3:
        context = new IOContext(new MergeInfo(randomNumDocs, size, true, -1));
        break;
      case 4:
        context = new IOContext(new FlushInfo(randomNumDocs, size));
        break;
      default:
        context = IOContext.DEFAULT;
      }
      return context;
    }
  }

  private static final QueryCache DEFAULT_QUERY_CACHE = IndexSearcher.getDefaultQueryCache();
  private static final QueryCachingPolicy DEFAULT_CACHING_POLICY = IndexSearcher.getDefaultQueryCachingPolicy();

  @Before
  public void overrideTestDefaultQueryCache() {
    // Make sure each test method has its own cache
    overrideDefaultQueryCache();
  }

  @BeforeClass
  public static void overrideDefaultQueryCache() {
    // we need to reset the query cache in an @BeforeClass so that tests that
    // instantiate an IndexSearcher in an @BeforeClass method use a fresh new cache
    IndexSearcher.setDefaultQueryCache(new LRUQueryCache(10000, 1 << 25, context -> true, Float.POSITIVE_INFINITY));
    IndexSearcher.setDefaultQueryCachingPolicy(MAYBE_CACHE_POLICY);
  }

  @AfterClass
  public static void resetDefaultQueryCache() {
    IndexSearcher.setDefaultQueryCache(DEFAULT_QUERY_CACHE);
    IndexSearcher.setDefaultQueryCachingPolicy(DEFAULT_CACHING_POLICY);
  }

  @BeforeClass
  public static void setupCPUCoreCount() {
    // Randomize core count so CMS varies its dynamic defaults, and this also "fixes" core
    // count from the master seed so it will always be the same on reproduce:
    int numCores = TestUtil.nextInt(random(), 1, 4);
    System.setProperty(ConcurrentMergeScheduler.DEFAULT_CPU_CORE_COUNT_PROPERTY, Integer.toString(numCores));
  }

  @AfterClass
  public static void restoreCPUCoreCount() {
    System.clearProperty(ConcurrentMergeScheduler.DEFAULT_CPU_CORE_COUNT_PROPERTY);
  }

  @BeforeClass
  public static void setupSpins() {
    // Randomize IOUtils.spins() count so CMS varies its dynamic defaults, and this also "fixes" core
    // count from the master seed so it will always be the same on reproduce:
    boolean spins = random().nextBoolean();
    System.setProperty(ConcurrentMergeScheduler.DEFAULT_SPINS_PROPERTY, Boolean.toString(spins));
  }

  @AfterClass
  public static void restoreSpins() {
    System.clearProperty(ConcurrentMergeScheduler.DEFAULT_SPINS_PROPERTY);
  }

  /**
   * Create a new searcher over the reader. This searcher might randomly use
   * threads.
   */
  public static IndexSearcher newSearcher(IndexReader r) {
    return newSearcher(r, true);
  }

  /**
   * Create a new searcher over the reader. This searcher might randomly use
   * threads.
   */
  public static IndexSearcher newSearcher(IndexReader r, boolean maybeWrap) {
    return newSearcher(r, maybeWrap, true);
  }

  /**
   * Create a new searcher over the reader. This searcher might randomly use
   * threads. if <code>maybeWrap</code> is true, this searcher might wrap the
   * reader with one that returns null for getSequentialSubReaders. If
   * <code>wrapWithAssertions</code> is true, this searcher might be an
   * {@link AssertingIndexSearcher} instance.
   */
  public static IndexSearcher newSearcher(IndexReader r, boolean maybeWrap, boolean wrapWithAssertions) {
    Random random = random();
    if (usually()) {
      if (maybeWrap) {
        try {
          r = maybeWrapReader(r);
        } catch (IOException e) {
          Rethrow.rethrow(e);
        }
      }
      // TODO: this whole check is a coverage hack, we should move it to tests for various filterreaders.
      // ultimately whatever you do will be checkIndex'd at the end anyway. 
      if (random.nextInt(500) == 0 && r instanceof LeafReader) {
        // TODO: not useful to check DirectoryReader (redundant with checkindex)
        // but maybe sometimes run this on the other crazy readers maybeWrapReader creates?
        try {
          TestUtil.checkReader(r);
        } catch (IOException e) {
          Rethrow.rethrow(e);
        }
      }
      final IndexSearcher ret;
      if (wrapWithAssertions) {
        ret = random.nextBoolean() ? new AssertingIndexSearcher(random, r) : new AssertingIndexSearcher(random, r.getContext());
      } else {
        ret = random.nextBoolean() ? new IndexSearcher(r) : new IndexSearcher(r.getContext());
      }
      ret.setSimilarity(classEnvRule.similarity);
      return ret;
    } else {
      int threads = 0;
      final ThreadPoolExecutor ex;
      if (r.getReaderCacheHelper() == null || random.nextBoolean()) {
        ex = null;
      } else {
        threads = TestUtil.nextInt(random, 1, 8);
        ex = new ThreadPoolExecutor(threads, threads, 0L, TimeUnit.MILLISECONDS,
            new LinkedBlockingQueue<Runnable>(),
            new NamedThreadFactory("LuceneTestCase"));
        // uncomment to intensify LUCENE-3840
        // ex.prestartAllCoreThreads();
      }
      if (ex != null) {
       if (VERBOSE) {
         System.out.println("NOTE: newSearcher using ExecutorService with " + threads + " threads");
       }
       r.getReaderCacheHelper().addClosedListener(cacheKey -> TestUtil.shutdownExecutorService(ex));
      }
      IndexSearcher ret;
      if (wrapWithAssertions) {
        ret = random.nextBoolean()
            ? new AssertingIndexSearcher(random, r, ex)
            : new AssertingIndexSearcher(random, r.getContext(), ex);
      } else {
        ret = random.nextBoolean()
            ? new IndexSearcher(r, ex)
            : new IndexSearcher(r.getContext(), ex);
      }
      ret.setSimilarity(classEnvRule.similarity);
      ret.setQueryCachingPolicy(MAYBE_CACHE_POLICY);
      return ret;
    }
  }

  /**
   * Gets a resource from the test's classpath as {@link Path}. This method should only
   * be used, if a real file is needed. To get a stream, code should prefer
   * {@link #getDataInputStream(String)}.
   */
  protected Path getDataPath(String name) throws IOException {
    try {
      return Paths.get(this.getClass().getResource(name).toURI());
    } catch (Exception e) {
      throw new IOException("Cannot find resource: " + name);
    }
  }

  /**
   * Gets a resource from the test's classpath as {@link InputStream}.
   */
  protected InputStream getDataInputStream(String name) throws IOException {
    InputStream in = this.getClass().getResourceAsStream(name);
    if (in == null) {
      throw new IOException("Cannot find resource: " + name);
    }
    return in;
  }

  public void assertReaderEquals(String info, IndexReader leftReader, IndexReader rightReader) throws IOException {
    assertReaderStatisticsEquals(info, leftReader, rightReader);
    assertTermsEquals(info, leftReader, rightReader, true);
    assertNormsEquals(info, leftReader, rightReader);
    assertStoredFieldsEquals(info, leftReader, rightReader);
    assertTermVectorsEquals(info, leftReader, rightReader);
    assertDocValuesEquals(info, leftReader, rightReader);
    assertDeletedDocsEquals(info, leftReader, rightReader);
    assertFieldInfosEquals(info, leftReader, rightReader);
    assertPointsEquals(info, leftReader, rightReader);
  }

  /** 
   * checks that reader-level statistics are the same 
   */
  public void assertReaderStatisticsEquals(String info, IndexReader leftReader, IndexReader rightReader) throws IOException {
    // Somewhat redundant: we never delete docs
    assertEquals(info, leftReader.maxDoc(), rightReader.maxDoc());
    assertEquals(info, leftReader.numDocs(), rightReader.numDocs());
    assertEquals(info, leftReader.numDeletedDocs(), rightReader.numDeletedDocs());
    assertEquals(info, leftReader.hasDeletions(), rightReader.hasDeletions());
  }

  /** 
   * Fields api equivalency 
   */
  public void assertTermsEquals(String info, IndexReader leftReader, IndexReader rightReader, boolean deep) throws IOException {
    Set<String> leftFields = new HashSet<>(FieldInfos.getIndexedFields(leftReader));
    Set<String> rightFields = new HashSet<>(FieldInfos.getIndexedFields(rightReader));
    assertEquals(info, leftFields, rightFields);

    for (String field : leftFields) {
      assertTermsEquals(info, leftReader, MultiTerms.getTerms(leftReader, field), MultiTerms.getTerms(rightReader, field), deep);
    }
  }

  /** 
   * Terms api equivalency 
   */
  public void assertTermsEquals(String info, IndexReader leftReader, Terms leftTerms, Terms rightTerms, boolean deep) throws IOException {
    if (leftTerms == null || rightTerms == null) {
      assertNull(info, leftTerms);
      assertNull(info, rightTerms);
      return;
    }
    assertTermsStatisticsEquals(info, leftTerms, rightTerms);
    assertEquals("hasOffsets", leftTerms.hasOffsets(), rightTerms.hasOffsets());
    assertEquals("hasPositions", leftTerms.hasPositions(), rightTerms.hasPositions());
    assertEquals("hasPayloads", leftTerms.hasPayloads(), rightTerms.hasPayloads());

    TermsEnum leftTermsEnum = leftTerms.iterator();
    TermsEnum rightTermsEnum = rightTerms.iterator();
    assertTermsEnumEquals(info, leftReader, leftTermsEnum, rightTermsEnum, true);
    
    assertTermsSeekingEquals(info, leftTerms, rightTerms);
    
    if (deep) {
      int numIntersections = atLeast(3);
      for (int i = 0; i < numIntersections; i++) {
        String re = AutomatonTestUtil.randomRegexp(random());
        CompiledAutomaton automaton = new CompiledAutomaton(new RegExp(re, RegExp.NONE).toAutomaton());
        if (automaton.type == CompiledAutomaton.AUTOMATON_TYPE.NORMAL) {
          // TODO: test start term too
          TermsEnum leftIntersection = leftTerms.intersect(automaton, null);
          TermsEnum rightIntersection = rightTerms.intersect(automaton, null);
          assertTermsEnumEquals(info, leftReader, leftIntersection, rightIntersection, rarely());
        }
      }
    }
  }

  /** 
   * checks collection-level statistics on Terms 
   */
  public void assertTermsStatisticsEquals(String info, Terms leftTerms, Terms rightTerms) throws IOException {
    assertEquals(info, leftTerms.getDocCount(), rightTerms.getDocCount());
    assertEquals(info, leftTerms.getSumDocFreq(), rightTerms.getSumDocFreq());
    assertEquals(info, leftTerms.getSumTotalTermFreq(), rightTerms.getSumTotalTermFreq());
    if (leftTerms.size() != -1 && rightTerms.size() != -1) {
      assertEquals(info, leftTerms.size(), rightTerms.size());
    }
  }

  private static class RandomBits implements Bits {
    FixedBitSet bits;
    
    RandomBits(int maxDoc, double pctLive, Random random) {
      bits = new FixedBitSet(maxDoc);
      for (int i = 0; i < maxDoc; i++) {
        if (random.nextDouble() <= pctLive) {        
          bits.set(i);
        }
      }
    }
    
    @Override
    public boolean get(int index) {
      return bits.get(index);
    }

    @Override
    public int length() {
      return bits.length();
    }
  }

  /** 
   * checks the terms enum sequentially
   * if deep is false, it does a 'shallow' test that doesnt go down to the docsenums
   */
  public void assertTermsEnumEquals(String info, IndexReader leftReader, TermsEnum leftTermsEnum, TermsEnum rightTermsEnum, boolean deep) throws IOException {
    BytesRef term;
    PostingsEnum leftPositions = null;
    PostingsEnum rightPositions = null;
    PostingsEnum leftDocs = null;
    PostingsEnum rightDocs = null;
    
    while ((term = leftTermsEnum.next()) != null) {
      assertEquals(info, term, rightTermsEnum.next());
      assertTermStatsEquals(info, leftTermsEnum, rightTermsEnum);
      if (deep) {
        assertDocsAndPositionsEnumEquals(info, leftPositions = leftTermsEnum.postings(leftPositions, PostingsEnum.ALL),
                                   rightPositions = rightTermsEnum.postings(rightPositions, PostingsEnum.ALL));

        assertPositionsSkippingEquals(info, leftReader, leftTermsEnum.docFreq(), 
                                leftPositions = leftTermsEnum.postings(leftPositions, PostingsEnum.ALL),
                                rightPositions = rightTermsEnum.postings(rightPositions, PostingsEnum.ALL));


        // with freqs:
        assertDocsEnumEquals(info, leftDocs = leftTermsEnum.postings(leftDocs),
            rightDocs = rightTermsEnum.postings(rightDocs),
            true);


        // w/o freqs:
        assertDocsEnumEquals(info, leftDocs = leftTermsEnum.postings(leftDocs, PostingsEnum.NONE),
            rightDocs = rightTermsEnum.postings(rightDocs, PostingsEnum.NONE),
            false);

        
        // with freqs:
        assertDocsSkippingEquals(info, leftReader, leftTermsEnum.docFreq(), 
            leftDocs = leftTermsEnum.postings(leftDocs),
            rightDocs = rightTermsEnum.postings(rightDocs),
            true);

        // w/o freqs:
        assertDocsSkippingEquals(info, leftReader, leftTermsEnum.docFreq(), 
            leftDocs = leftTermsEnum.postings(leftDocs, PostingsEnum.NONE),
            rightDocs = rightTermsEnum.postings(rightDocs, PostingsEnum.NONE),
            false);
      }
    }
    assertNull(info, rightTermsEnum.next());
  }


  /**
   * checks docs + freqs + positions + payloads, sequentially
   */
  public void assertDocsAndPositionsEnumEquals(String info, PostingsEnum leftDocs, PostingsEnum rightDocs) throws IOException {
    assertNotNull(leftDocs);
    assertNotNull(rightDocs);
    assertEquals(info, -1, leftDocs.docID());
    assertEquals(info, -1, rightDocs.docID());
    int docid;
    while ((docid = leftDocs.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
      assertEquals(info, docid, rightDocs.nextDoc());
      int freq = leftDocs.freq();
      assertEquals(info, freq, rightDocs.freq());
      for (int i = 0; i < freq; i++) {
        assertEquals(info, leftDocs.nextPosition(), rightDocs.nextPosition());
        assertEquals(info, leftDocs.getPayload(), rightDocs.getPayload());
        assertEquals(info, leftDocs.startOffset(), rightDocs.startOffset());
        assertEquals(info, leftDocs.endOffset(), rightDocs.endOffset());
      }
    }
    assertEquals(info, DocIdSetIterator.NO_MORE_DOCS, rightDocs.nextDoc());
  }
  
  /**
   * checks docs + freqs, sequentially
   */
  public void assertDocsEnumEquals(String info, PostingsEnum leftDocs, PostingsEnum rightDocs, boolean hasFreqs) throws IOException {
    if (leftDocs == null) {
      assertNull(rightDocs);
      return;
    }
    assertEquals(info, -1, leftDocs.docID());
    assertEquals(info, -1, rightDocs.docID());
    int docid;
    while ((docid = leftDocs.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
      assertEquals(info, docid, rightDocs.nextDoc());
      if (hasFreqs) {
        assertEquals(info, leftDocs.freq(), rightDocs.freq());
      }
    }
    assertEquals(info, DocIdSetIterator.NO_MORE_DOCS, rightDocs.nextDoc());
  }
  
  /**
   * checks advancing docs
   */
  public void assertDocsSkippingEquals(String info, IndexReader leftReader, int docFreq, PostingsEnum leftDocs, PostingsEnum rightDocs, boolean hasFreqs) throws IOException {
    if (leftDocs == null) {
      assertNull(rightDocs);
      return;
    }
    int docid = -1;
    int averageGap = leftReader.maxDoc() / (1+docFreq);
    int skipInterval = 16;

    while (true) {
      if (random().nextBoolean()) {
        // nextDoc()
        docid = leftDocs.nextDoc();
        assertEquals(info, docid, rightDocs.nextDoc());
      } else {
        // advance()
        int skip = docid + (int) Math.ceil(Math.abs(skipInterval + random().nextGaussian() * averageGap));
        docid = leftDocs.advance(skip);
        assertEquals(info, docid, rightDocs.advance(skip));
      }
      
      if (docid == DocIdSetIterator.NO_MORE_DOCS) {
        return;
      }
      if (hasFreqs) {
        assertEquals(info, leftDocs.freq(), rightDocs.freq());
      }
    }
  }
  
  /**
   * checks advancing docs + positions
   */
  public void assertPositionsSkippingEquals(String info, IndexReader leftReader, int docFreq, PostingsEnum leftDocs, PostingsEnum rightDocs) throws IOException {
    if (leftDocs == null || rightDocs == null) {
      assertNull(leftDocs);
      assertNull(rightDocs);
      return;
    }
    
    int docid = -1;
    int averageGap = leftReader.maxDoc() / (1+docFreq);
    int skipInterval = 16;

    while (true) {
      if (random().nextBoolean()) {
        // nextDoc()
        docid = leftDocs.nextDoc();
        assertEquals(info, docid, rightDocs.nextDoc());
      } else {
        // advance()
        int skip = docid + (int) Math.ceil(Math.abs(skipInterval + random().nextGaussian() * averageGap));
        docid = leftDocs.advance(skip);
        assertEquals(info, docid, rightDocs.advance(skip));
      }
      
      if (docid == DocIdSetIterator.NO_MORE_DOCS) {
        return;
      }
      int freq = leftDocs.freq();
      assertEquals(info, freq, rightDocs.freq());
      for (int i = 0; i < freq; i++) {
        assertEquals(info, leftDocs.nextPosition(), rightDocs.nextPosition());
        assertEquals(info, leftDocs.getPayload(), rightDocs.getPayload());
      }
    }
  }

  
  private void assertTermsSeekingEquals(String info, Terms leftTerms, Terms rightTerms) throws IOException {

    // just an upper bound
    int numTests = atLeast(20);
    Random random = random();

    TermsEnum leftEnum = null;

    // collect this number of terms from the left side
    HashSet<BytesRef> tests = new HashSet<>();
    int numPasses = 0;
    while (numPasses < 10 && tests.size() < numTests) {
      leftEnum = leftTerms.iterator();
      BytesRef term = null;
      while ((term = leftEnum.next()) != null) {
        int code = random.nextInt(10);
        if (code == 0) {
          // the term
          tests.add(BytesRef.deepCopyOf(term));
        } else if (code == 1) {
          // truncated subsequence of term
          term = BytesRef.deepCopyOf(term);
          if (term.length > 0) {
            // truncate it
            term.length = random.nextInt(term.length);
          }
        } else if (code == 2) {
          // term, but ensure a non-zero offset
          byte newbytes[] = new byte[term.length+5];
          System.arraycopy(term.bytes, term.offset, newbytes, 5, term.length);
          tests.add(new BytesRef(newbytes, 5, term.length));
        } else if (code == 3) {
          switch (random().nextInt(3)) {
            case 0:
              tests.add(new BytesRef()); // before the first term
              break;
            case 1:
              tests.add(new BytesRef(new byte[] {(byte) 0xFF, (byte) 0xFF})); // past the last term
              break;
            case 2:
              tests.add(new BytesRef(TestUtil.randomSimpleString(random()))); // random term
              break;
            default:
              throw new AssertionError();
          }
        }
      }
      numPasses++;
    }

    TermsEnum rightEnum = rightTerms.iterator();

    ArrayList<BytesRef> shuffledTests = new ArrayList<>(tests);
    Collections.shuffle(shuffledTests, random);

    for (BytesRef b : shuffledTests) {
      if (rarely()) {
        // make new enums
        leftEnum = leftTerms.iterator();
        rightEnum = rightTerms.iterator();
      }

      final boolean seekExact = random().nextBoolean();

      if (seekExact) {
        assertEquals(info, leftEnum.seekExact(b), rightEnum.seekExact(b));
      } else {
        SeekStatus leftStatus = leftEnum.seekCeil(b);
        SeekStatus rightStatus = rightEnum.seekCeil(b);
        assertEquals(info, leftStatus, rightStatus);
        if (leftStatus != SeekStatus.END) {
          assertEquals(info, leftEnum.term(), rightEnum.term());
          assertTermStatsEquals(info, leftEnum, rightEnum);
        }
      }
    }
  }
  
  /**
   * checks term-level statistics
   */
  public void assertTermStatsEquals(String info, TermsEnum leftTermsEnum, TermsEnum rightTermsEnum) throws IOException {
    assertEquals(info, leftTermsEnum.docFreq(), rightTermsEnum.docFreq());
    assertEquals(info, leftTermsEnum.totalTermFreq(), rightTermsEnum.totalTermFreq());
  }
  
  /** 
   * checks that norms are the same across all fields 
   */
  public void assertNormsEquals(String info, IndexReader leftReader, IndexReader rightReader) throws IOException {
    Set<String> leftFields = new HashSet<>(FieldInfos.getIndexedFields(leftReader));
    Set<String> rightFields = new HashSet<>(FieldInfos.getIndexedFields(rightReader));
    assertEquals(info, leftFields, rightFields);
    
    for (String field : leftFields) {
      NumericDocValues leftNorms = MultiDocValues.getNormValues(leftReader, field);
      NumericDocValues rightNorms = MultiDocValues.getNormValues(rightReader, field);
      if (leftNorms != null && rightNorms != null) {
        assertDocValuesEquals(info, leftReader.maxDoc(), leftNorms, rightNorms);
      } else {
        assertNull(info, leftNorms);
        assertNull(info, rightNorms);
      }
    }
  }
  
  /** 
   * checks that stored fields of all documents are the same 
   */
  public void assertStoredFieldsEquals(String info, IndexReader leftReader, IndexReader rightReader) throws IOException {
    assert leftReader.maxDoc() == rightReader.maxDoc();
    for (int i = 0; i < leftReader.maxDoc(); i++) {
      Document leftDoc = leftReader.document(i);
      Document rightDoc = rightReader.document(i);
      
      // TODO: I think this is bogus because we don't document what the order should be
      // from these iterators, etc. I think the codec/IndexReader should be free to order this stuff
      // in whatever way it wants (e.g. maybe it packs related fields together or something)
      // To fix this, we sort the fields in both documents by name, but
      // we still assume that all instances with same name are in order:
      Comparator<IndexableField> comp = new Comparator<IndexableField>() {
        @Override
        public int compare(IndexableField arg0, IndexableField arg1) {
          return arg0.name().compareTo(arg1.name());
        }        
      };
      List<IndexableField> leftFields = new ArrayList<>(leftDoc.getFields());
      List<IndexableField> rightFields = new ArrayList<>(rightDoc.getFields());
      Collections.sort(leftFields, comp);
      Collections.sort(rightFields, comp);

      Iterator<IndexableField> leftIterator = leftFields.iterator();
      Iterator<IndexableField> rightIterator = rightFields.iterator();
      while (leftIterator.hasNext()) {
        assertTrue(info, rightIterator.hasNext());
        assertStoredFieldEquals(info, leftIterator.next(), rightIterator.next());
      }
      assertFalse(info, rightIterator.hasNext());
    }
  }
  
  /** 
   * checks that two stored fields are equivalent 
   */
  public void assertStoredFieldEquals(String info, IndexableField leftField, IndexableField rightField) {
    assertEquals(info, leftField.name(), rightField.name());
    assertEquals(info, leftField.binaryValue(), rightField.binaryValue());
    assertEquals(info, leftField.stringValue(), rightField.stringValue());
    assertEquals(info, leftField.numericValue(), rightField.numericValue());
    // TODO: should we check the FT at all?
  }
  
  /** 
   * checks that term vectors across all fields are equivalent 
   */
  public void assertTermVectorsEquals(String info, IndexReader leftReader, IndexReader rightReader) throws IOException {
    assert leftReader.maxDoc() == rightReader.maxDoc();
    for (int i = 0; i < leftReader.maxDoc(); i++) {
      Fields leftFields = leftReader.getTermVectors(i);
      Fields rightFields = rightReader.getTermVectors(i);

      // Fields could be null if there are no postings,
      // but then it must be null for both
      if (leftFields == null || rightFields == null) {
        assertNull(info, leftFields);
        assertNull(info, rightFields);
        return;
      }
      if (leftFields.size() != -1 && rightFields.size() != -1) {
        assertEquals(info, leftFields.size(), rightFields.size());
      }

      Iterator<String> leftEnum = leftFields.iterator();
      Iterator<String> rightEnum = rightFields.iterator();
      while (leftEnum.hasNext()) {
        String field = leftEnum.next();
        assertEquals(info, field, rightEnum.next());
        assertTermsEquals(info, leftReader, leftFields.terms(field), rightFields.terms(field), rarely());
      }
      assertFalse(rightEnum.hasNext());
    }
  }

  private static Set<String> getDVFields(IndexReader reader) {
    Set<String> fields = new HashSet<>();
    for(FieldInfo fi : FieldInfos.getMergedFieldInfos(reader)) {
      if (fi.getDocValuesType() != DocValuesType.NONE) {
        fields.add(fi.name);
      }
    }

    return fields;
  }
  
  /**
   * checks that docvalues across all fields are equivalent
   */
  public void assertDocValuesEquals(String info, IndexReader leftReader, IndexReader rightReader) throws IOException {
    Set<String> leftFields = getDVFields(leftReader);
    Set<String> rightFields = getDVFields(rightReader);
    assertEquals(info, leftFields, rightFields);

    for (String field : leftFields) {
      // TODO: clean this up... very messy
      {
        NumericDocValues leftValues = MultiDocValues.getNumericValues(leftReader, field);
        NumericDocValues rightValues = MultiDocValues.getNumericValues(rightReader, field);
        if (leftValues != null && rightValues != null) {
          assertDocValuesEquals(info, leftReader.maxDoc(), leftValues, rightValues);
        } else {
          assertTrue(info + ": left numeric doc values for field=\"" + field + "\" are not null", leftValues == null || leftValues.nextDoc() == NO_MORE_DOCS);
          assertTrue(info + ": right numeric doc values for field=\"" + field + "\" are not null", rightValues == null || rightValues.nextDoc() == NO_MORE_DOCS);
        }
      }

      {
        BinaryDocValues leftValues = MultiDocValues.getBinaryValues(leftReader, field);
        BinaryDocValues rightValues = MultiDocValues.getBinaryValues(rightReader, field);
        if (leftValues != null && rightValues != null) {
          while (true) {
            int docID = leftValues.nextDoc();
            assertEquals(docID, rightValues.nextDoc());
            if (docID == NO_MORE_DOCS) {
              break;
            }
            assertEquals(leftValues.binaryValue(), rightValues.binaryValue());
          }
        } else {
          assertTrue(info, leftValues == null || leftValues.nextDoc() == NO_MORE_DOCS);
          assertTrue(info, rightValues == null || rightValues.nextDoc() == NO_MORE_DOCS);
        }
      }
      
      {
        SortedDocValues leftValues = MultiDocValues.getSortedValues(leftReader, field);
        SortedDocValues rightValues = MultiDocValues.getSortedValues(rightReader, field);
        if (leftValues != null && rightValues != null) {
          // numOrds
          assertEquals(info, leftValues.getValueCount(), rightValues.getValueCount());
          // ords
          for (int i = 0; i < leftValues.getValueCount(); i++) {
            final BytesRef left = BytesRef.deepCopyOf(leftValues.lookupOrd(i));
            final BytesRef right = rightValues.lookupOrd(i);
            assertEquals(info, left, right);
          }
          // bytes
          for(int docID=0;docID<leftReader.maxDoc();docID++) {
            assertEquals(docID, leftValues.nextDoc());
            assertEquals(docID, rightValues.nextDoc());
            final BytesRef left = BytesRef.deepCopyOf(leftValues.binaryValue());
            final BytesRef right = rightValues.binaryValue();
            assertEquals(info, left, right);
          }
        } else {
          assertNull(info, leftValues);
          assertNull(info, rightValues);
        }
      }
      
      {
        SortedSetDocValues leftValues = MultiDocValues.getSortedSetValues(leftReader, field);
        SortedSetDocValues rightValues = MultiDocValues.getSortedSetValues(rightReader, field);
        if (leftValues != null && rightValues != null) {
          // numOrds
          assertEquals(info, leftValues.getValueCount(), rightValues.getValueCount());
          // ords
          for (int i = 0; i < leftValues.getValueCount(); i++) {
            final BytesRef left = BytesRef.deepCopyOf(leftValues.lookupOrd(i));
            final BytesRef right = rightValues.lookupOrd(i);
            assertEquals(info, left, right);
          }
          // ord lists
          while (true) {
            int docID = leftValues.nextDoc();
            assertEquals(docID, rightValues.nextDoc());
            if (docID == NO_MORE_DOCS) {
              break;
            }
            long ord;
            while ((ord = leftValues.nextOrd()) != SortedSetDocValues.NO_MORE_ORDS) {
              assertEquals(info, ord, rightValues.nextOrd());
            }
            assertEquals(info, SortedSetDocValues.NO_MORE_ORDS, rightValues.nextOrd());
          }
        } else {
          assertNull(info, leftValues);
          assertNull(info, rightValues);
        }
      }
      
      {
        SortedNumericDocValues leftValues = MultiDocValues.getSortedNumericValues(leftReader, field);
        SortedNumericDocValues rightValues = MultiDocValues.getSortedNumericValues(rightReader, field);
        if (leftValues != null && rightValues != null) {
          while (true) {
            int docID = leftValues.nextDoc();
            assertEquals(docID, rightValues.nextDoc());
            if (docID == NO_MORE_DOCS) {
              break;
            }
            assertEquals(info, leftValues.docValueCount(), rightValues.docValueCount());
            for (int j = 0; j < leftValues.docValueCount(); j++) {
              assertEquals(info, leftValues.nextValue(), rightValues.nextValue());
            }
          }
        } else {
          assertNull(info, leftValues);
          assertNull(info, rightValues);
        }
      }
    }
  }
  
  public void assertDocValuesEquals(String info, int num, NumericDocValues leftDocValues, NumericDocValues rightDocValues) throws IOException {
    assertNotNull(info, leftDocValues);
    assertNotNull(info, rightDocValues);
    while (true) {
      int leftDocID = leftDocValues.nextDoc();
      int rightDocID = rightDocValues.nextDoc();
      assertEquals(leftDocID, rightDocID);
      if (leftDocID == NO_MORE_DOCS) {
        return;
      }
      assertEquals(leftDocValues.longValue(), rightDocValues.longValue());
    }
  }
  
  // TODO: this is kinda stupid, we don't delete documents in the test.
  public void assertDeletedDocsEquals(String info, IndexReader leftReader, IndexReader rightReader) throws IOException {
    assert leftReader.numDeletedDocs() == rightReader.numDeletedDocs();
    Bits leftBits = MultiBits.getLiveDocs(leftReader);
    Bits rightBits = MultiBits.getLiveDocs(rightReader);
    
    if (leftBits == null || rightBits == null) {
      assertNull(info, leftBits);
      assertNull(info, rightBits);
      return;
    }
    
    assert leftReader.maxDoc() == rightReader.maxDoc();
    assertEquals(info, leftBits.length(), rightBits.length());
    for (int i = 0; i < leftReader.maxDoc(); i++) {
      assertEquals(info, leftBits.get(i), rightBits.get(i));
    }
  }
  
  public void assertFieldInfosEquals(String info, IndexReader leftReader, IndexReader rightReader) throws IOException {
    FieldInfos leftInfos = FieldInfos.getMergedFieldInfos(leftReader);
    FieldInfos rightInfos = FieldInfos.getMergedFieldInfos(rightReader);
    
    // TODO: would be great to verify more than just the names of the fields!
    TreeSet<String> left = new TreeSet<>();
    TreeSet<String> right = new TreeSet<>();
    
    for (FieldInfo fi : leftInfos) {
      left.add(fi.name);
    }
    
    for (FieldInfo fi : rightInfos) {
      right.add(fi.name);
    }
    
    assertEquals(info, left, right);
  }

  // naive silly memory heavy uninversion!!  maps docID -> packed values (a Set because a given doc can be multi-valued)
  private Map<Integer,Set<BytesRef>> uninvert(String fieldName, IndexReader reader) throws IOException {
    final Map<Integer,Set<BytesRef>> docValues = new HashMap<>();
    for(LeafReaderContext ctx : reader.leaves()) {

      PointValues points = ctx.reader().getPointValues(fieldName);
      if (points == null) {
        continue;
      }

      points.intersect(
                       new PointValues.IntersectVisitor() {
                         @Override
                         public void visit(int docID) {
                           throw new UnsupportedOperationException();
                         }

                         @Override
                         public void visit(int docID, byte[] packedValue) throws IOException {
                           int topDocID = ctx.docBase + docID;
                           if (docValues.containsKey(topDocID) == false) {
                             docValues.put(topDocID, new HashSet<BytesRef>());
                           }
                           docValues.get(topDocID).add(new BytesRef(packedValue.clone()));
                         }

                         @Override
                         public PointValues.Relation compare(byte[] minPackedValue, byte[] maxPackedValue) {
                           // We pretend our query shape is so hairy that it crosses every single cell:
                           return PointValues.Relation.CELL_CROSSES_QUERY;
                         }
                       });
    }

    return docValues;
  }

  public void assertPointsEquals(String info, IndexReader leftReader, IndexReader rightReader) throws IOException {
    FieldInfos fieldInfos1 = FieldInfos.getMergedFieldInfos(leftReader);
    FieldInfos fieldInfos2 = FieldInfos.getMergedFieldInfos(rightReader);
    for(FieldInfo fieldInfo1 : fieldInfos1) {
      if (fieldInfo1.getPointDimensionCount() != 0) {
        FieldInfo fieldInfo2 = fieldInfos2.fieldInfo(fieldInfo1.name);
        // same data dimension count?
        assertEquals(info, fieldInfo2.getPointDimensionCount(), fieldInfo2.getPointDimensionCount());
        // same index dimension count?
        assertEquals(info, fieldInfo2.getPointIndexDimensionCount(), fieldInfo2.getPointIndexDimensionCount());
        // same bytes per dimension?
        assertEquals(info, fieldInfo2.getPointNumBytes(), fieldInfo2.getPointNumBytes());

        assertEquals(info + " field=" + fieldInfo1.name,
                     uninvert(fieldInfo1.name, leftReader),
                     uninvert(fieldInfo1.name, rightReader));
      }
    }

    // make sure FieldInfos2 doesn't have any point fields that FieldInfo1 didn't have
    for(FieldInfo fieldInfo2 : fieldInfos2) {
      if (fieldInfo2.getPointDimensionCount() != 0) {
        FieldInfo fieldInfo1 = fieldInfos1.fieldInfo(fieldInfo2.name);
        // same data dimension count?
        assertEquals(info, fieldInfo2.getPointDimensionCount(), fieldInfo1.getPointDimensionCount());
        // same index dimension count?
        assertEquals(info, fieldInfo2.getPointIndexDimensionCount(), fieldInfo1.getPointIndexDimensionCount());
        // same bytes per dimension?
        assertEquals(info, fieldInfo2.getPointNumBytes(), fieldInfo1.getPointNumBytes());

        // we don't need to uninvert and compare here ... we did that in the first loop above
      }
    }
  }
  
  /** Inspects stack trace to figure out if a method of a specific class called us. */
  public static boolean callStackContains(Class<?> clazz, String methodName) {
    final String className = clazz.getName();
    return Stream.of(new Exception().getStackTrace()).skip(1) // exclude this utility method
        .anyMatch(f -> className.equals(f.getClassName()) && methodName.equals(f.getMethodName()));
  }

  /** Inspects stack trace to figure out if one of the given method names (no class restriction) called us. */
  public static boolean callStackContainsAnyOf(String... methodNames) {
    return Stream.of(new Exception().getStackTrace()).skip(1) // exclude this utility method
        .map(StackTraceElement::getMethodName)
        .anyMatch(Arrays.asList(methodNames)::contains);
  }

  /** Inspects stack trace if the given class called us. */
  public static boolean callStackContains(Class<?> clazz) {
    return Stream.of(new Exception().getStackTrace()).skip(1) // exclude this utility method
        .map(StackTraceElement::getClassName)
        .anyMatch(clazz.getName()::equals);
  }

  /** A runnable that can throw any checked exception. */
  @FunctionalInterface
  public interface ThrowingRunnable {
    void run() throws Throwable;
  }

  /** Checks a specific exception class is thrown by the given runnable, and returns it. */
  public static <T extends Throwable> T expectThrows(Class<T> expectedType, ThrowingRunnable runnable) {
    return expectThrows(expectedType, "Expected exception "+ expectedType.getSimpleName() + " but no exception was thrown", runnable);
  }

  /** Checks a specific exception class is thrown by the given runnable, and returns it. */
  public static <T extends Throwable> T expectThrows(Class<T> expectedType, String noExceptionMessage, ThrowingRunnable runnable) {
    final Throwable thrown = _expectThrows(Collections.singletonList(expectedType), runnable);
    if (expectedType.isInstance(thrown)) {
      return expectedType.cast(thrown);
    }
    if (null == thrown) {
      throw new AssertionFailedError(noExceptionMessage);
    }
    AssertionFailedError assertion = new AssertionFailedError("Unexpected exception type, expected " + expectedType.getSimpleName() + " but got " + thrown);
    assertion.initCause(thrown);
    throw assertion;
  }

  /** Checks a specific exception class is thrown by the given runnable, and returns it. */
  public static <T extends Throwable> T expectThrowsAnyOf(List<Class<? extends T>> expectedTypes, ThrowingRunnable runnable) {
    if (expectedTypes.isEmpty()) {
      throw new AssertionError("At least one expected exception type is required?");
    }

    final Throwable thrown = _expectThrows(expectedTypes, runnable);
    if (null != thrown) {
      for (Class<? extends T> expectedType : expectedTypes) {
        if (expectedType.isInstance(thrown)) {
          return expectedType.cast(thrown);
        }
      }
    }

    List<String> exceptionTypes = expectedTypes.stream().map(c -> c.getSimpleName()).collect(Collectors.toList());

    if (thrown != null) {
      AssertionFailedError assertion = new AssertionFailedError("Unexpected exception type, expected any of " +
          exceptionTypes +
          " but got: " + thrown);
      assertion.initCause(thrown);
      throw assertion;
    } else {
      throw new AssertionFailedError("Expected any of the following exception types: " +
          exceptionTypes+ " but no exception was thrown.");
    }
  }

  /**
   * Checks that specific wrapped and outer exception classes are thrown
   * by the given runnable, and returns the wrapped exception. 
   */
  public static <TO extends Throwable, TW extends Throwable> TW expectThrows
  (Class<TO> expectedOuterType, Class<TW> expectedWrappedType, ThrowingRunnable runnable) {
    final Throwable thrown = _expectThrows(Collections.singletonList(expectedOuterType), runnable);
    if (null == thrown) {
      throw new AssertionFailedError("Expected outer exception " + expectedOuterType.getSimpleName()
                                     + " but no exception was thrown.");
    }
    if (expectedOuterType.isInstance(thrown)) {
      Throwable cause = thrown.getCause();
      if (expectedWrappedType.isInstance(cause)) {
        return expectedWrappedType.cast(cause);
      } else {
        AssertionFailedError assertion = new AssertionFailedError
          ("Unexpected wrapped exception type, expected " + expectedWrappedType.getSimpleName() 
           + " but got: " + cause);
        assertion.initCause(thrown);
        throw assertion;
      }
    }
    AssertionFailedError assertion = new AssertionFailedError
      ("Unexpected outer exception type, expected " + expectedOuterType.getSimpleName()
       + " but got: " + thrown);
    assertion.initCause(thrown);
    throw assertion;
  }

  /**
   * Checks that one of the specified wrapped and outer exception classes are thrown
   * by the given runnable, and returns the outer exception.
   * 
   * This method accepts outer exceptions with no wrapped exception;
   * an empty list of expected wrapped exception types indicates no wrapped exception.
   */
  public static <TO extends Throwable, TW extends Throwable> TO expectThrowsAnyOf
  (LinkedHashMap<Class<? extends TO>,List<Class<? extends TW>>> expectedOuterToWrappedTypes, ThrowingRunnable runnable) {
    final List<Class<? extends TO>> outerClasses = expectedOuterToWrappedTypes.keySet().stream().collect(Collectors.toList());
    final Throwable thrown = _expectThrows(outerClasses, runnable);
    
    if (null == thrown) {
      List<String> outerTypes = outerClasses.stream().map(Class::getSimpleName).collect(Collectors.toList());
      throw new AssertionFailedError("Expected any of the following outer exception types: " + outerTypes
                                     + " but no exception was thrown.");
    }
    for (Map.Entry<Class<? extends TO>, List<Class<? extends TW>>> entry : expectedOuterToWrappedTypes.entrySet()) {
      Class<? extends TO> expectedOuterType = entry.getKey();
      List<Class<? extends TW>> expectedWrappedTypes = entry.getValue();
      Throwable cause = thrown.getCause();
      if (expectedOuterType.isInstance(thrown)) {
        if (expectedWrappedTypes.isEmpty()) {
          return null; // no wrapped exception
        } else {
          for (Class<? extends TW> expectedWrappedType : expectedWrappedTypes) {
            if (expectedWrappedType.isInstance(cause)) {
              return expectedOuterType.cast(thrown);
            }
          }
          List<String> wrappedTypes = expectedWrappedTypes.stream().map(Class::getSimpleName).collect(Collectors.toList());
          AssertionFailedError assertion = new AssertionFailedError
            ("Unexpected wrapped exception type, expected one of " + wrappedTypes + " but got: " + cause);
          assertion.initCause(thrown);
          throw assertion;
        }
      }
    }
    List<String> outerTypes = outerClasses.stream().map(Class::getSimpleName).collect(Collectors.toList());
    AssertionFailedError assertion = new AssertionFailedError
      ("Unexpected outer exception type, expected one of " + outerTypes + " but got: " + thrown);
    assertion.initCause(thrown);
    throw assertion;
  }

  /**
   * Helper method for {@link #expectThrows} and {@link #expectThrowsAnyOf} that takes care of propagating
   * any {@link AssertionError} or {@link AssumptionViolatedException} instances thrown if and only if they 
   * are super classes of the <code>expectedTypes</code>.  Otherwise simply returns any {@link Throwable} 
   * thrown, regardless of type, or null if the <code>runnable</code> completed w/o error.
   */
  private static Throwable _expectThrows(List<? extends Class<?>> expectedTypes, ThrowingRunnable runnable) {
                                         
    try {
      runnable.run();
    } catch (AssertionError | AssumptionViolatedException ae) {
      for (Class<?> expectedType : expectedTypes) {
        if (expectedType.isInstance(ae)) { // user is expecting this type explicitly
          return ae;
        }
      }
      throw ae;
    } catch (Throwable e) {
      return e;
    }
    return null;
  }
  
  /** Returns true if the file exists (can be opened), false
   *  if it cannot be opened, and (unlike Java's
   *  File.exists) throws IOException if there's some
   *  unexpected error. */
  public static boolean slowFileExists(Directory dir, String fileName) throws IOException {
    try {
      dir.openInput(fileName, IOContext.DEFAULT).close();
      return true;
    } catch (NoSuchFileException | FileNotFoundException e) {
      return false;
    }
  }

  /**
   * This method is deprecated for a reason. Do not use it. Call {@link #createTempDir()}
   * or {@link #createTempDir(String)} or {@link #createTempFile(String, String)}.
   */
  @Deprecated
  public static Path getBaseTempDirForTestClass() {
    return tempFilesCleanupRule.getPerTestClassTempDir();
  }


  /**
   * Creates an empty, temporary folder (when the name of the folder is of no importance).
   * 
   * @see #createTempDir(String)
   */
  public static Path createTempDir() {
    return createTempDir("tempDir");
  }

  /**
   * Creates an empty, temporary folder with the given name prefix under the 
   * test class's {@link #getBaseTempDirForTestClass()}.
   *  
   * <p>The folder will be automatically removed after the
   * test class completes successfully. The test should close any file handles that would prevent
   * the folder from being removed. 
   */
  public static Path createTempDir(String prefix) {
    return tempFilesCleanupRule.createTempDir(prefix);
  }
  
  /**
   * Creates an empty file with the given prefix and suffix under the 
   * test class's {@link #getBaseTempDirForTestClass()}.
   * 
   * <p>The file will be automatically removed after the
   * test class completes successfully. The test should close any file handles that would prevent
   * the folder from being removed. 
   */
  public static Path createTempFile(String prefix, String suffix) throws IOException {
    return tempFilesCleanupRule.createTempFile(prefix, suffix);
  }

  /**
   * Creates an empty temporary file.
   * 
   * @see #createTempFile(String, String) 
   */
  public static Path createTempFile() throws IOException {
    return createTempFile("tempFile", ".tmp");
  }
  
  /** 
   * Runs a code part with restricted permissions (be sure to add all required permissions,
   * because it would start with empty permissions). You cannot grant more permissions than
   * our policy file allows, but you may restrict writing to several dirs...
   * <p><em>Note:</em> This assumes a {@link SecurityManager} enabled, otherwise it
   * stops test execution. If enabled, it needs the following {@link SecurityPermission}:
   * {@code "createAccessControlContext"}
   */
  public static <T> T runWithRestrictedPermissions(PrivilegedExceptionAction<T> action, Permission... permissions) throws Exception {
    assumeTrue("runWithRestrictedPermissions requires a SecurityManager enabled", System.getSecurityManager() != null);
    // be sure to have required permission, otherwise doPrivileged runs with *no* permissions:
    AccessController.checkPermission(new SecurityPermission("createAccessControlContext"));
    final PermissionCollection perms = new Permissions();
    Arrays.stream(permissions).forEach(perms::add);
    final AccessControlContext ctx = new AccessControlContext(new ProtectionDomain[] { new ProtectionDomain(null, perms) });
    try {
      return AccessController.doPrivileged(action, ctx);
    } catch (PrivilegedActionException e) {
      throw e.getException();
    }
  }

  /** True if assertions (-ea) are enabled (at least for this class). */
  public static final boolean assertsAreEnabled;

  static {
    boolean enabled = false;
    assert enabled = true; // Intentional side-effect!!!
    assertsAreEnabled = enabled;
  }
  
  /** 
   * Compares two strings with a collator, also looking to see if the the strings
   * are impacted by jdk bugs. may not avoid all jdk bugs in tests.
   * see https://bugs.openjdk.java.net/browse/JDK-8071862
   */
  @SuppressForbidden(reason = "dodges JDK-8071862")
  public static int collate(Collator collator, String s1, String s2) {
    int v1 = collator.compare(s1, s2);
    int v2 = collator.getCollationKey(s1).compareTo(collator.getCollationKey(s2));
    // if collation keys don't really respect collation order, things are screwed.
    assumeTrue("hit JDK collator bug", Integer.signum(v1) == Integer.signum(v2));
    return v1;
  }


  /**
   * Ensures that the MergePolicy has sane values for tests that test with lots of documents.
   */
  protected static IndexWriterConfig ensureSaneIWCOnNightly(IndexWriterConfig conf) {
    if (LuceneTestCase.TEST_NIGHTLY) {
      // newIWConfig makes smallish max seg size, which
      // results in tons and tons of segments for this test
      // when run nightly:
      MergePolicy mp = conf.getMergePolicy();
      if (mp instanceof TieredMergePolicy) {
        ((TieredMergePolicy) mp).setMaxMergedSegmentMB(5000.);
      } else if (mp instanceof LogByteSizeMergePolicy) {
        ((LogByteSizeMergePolicy) mp).setMaxMergeMB(1000.);
      } else if (mp instanceof LogMergePolicy) {
        ((LogMergePolicy) mp).setMaxMergeDocs(100000);
      }
      // when running nightly, merging can still have crazy parameters,
      // and might use many per-field codecs. turn on CFS for IW flushes
      // and ensure CFS ratio is reasonable to keep it contained.
      conf.setUseCompoundFile(true);
      mp.setNoCFSRatio(Math.max(0.25d, mp.getNoCFSRatio()));
    }
    return conf;
  }
}
