* @param valueEquivalence the equivalence relationship to use to compare values
   * @return the difference between the two maps
   * @since 10.0
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      MapDifference<K, V> difference(
          Map<? extends K, ? extends V> left,
          Map<? extends K, ? extends V> right,
          Equivalence<? super @NonNull V> valueEquivalence) {

   * @param valueEquivalence the equivalence relationship to use to compare values
   * @return the difference between the two maps
   * @since 10.0
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      MapDifference<K, V> difference(
          Map<? extends K, ? extends V> left,
          Map<? extends K, ? extends V> right,
          Equivalence<? super @NonNull V> valueEquivalence) {

    Map<Integer, String> right = ImmutableMap.of(1, "A", 3, "F", 5, "G", 6, "Z");

    // TODO(kevinb): replace with Ascii.caseInsensitiveEquivalence() when it
    // exists
    Equivalence<String> caseInsensitiveEquivalence =
        Equivalence.equals()
            .onResultOf(
                new Function<String, String>() {
                  @Override
                  public String apply(String input) {

import static org.mockito.ArgumentMatchers.isA;
import static org.mockito.Mockito.eq;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

import com.google.common.base.Equivalence;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;
import com.google.common.collect.testing.google.MultisetTestSuiteBuilder;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Equivalence;
import com.google.common.base.Function;
import com.google.common.collect.MapMaker.Dummy;
import com.google.common.collect.MapMakerInternalMap.InternalEntry;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertTrue;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Equivalence;
import com.google.common.collect.Iterables;
import com.google.common.testing.RelationshipTester.Item;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.ArrayList;
import java.util.List;

import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertTrue;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Equivalence;
import com.google.common.collect.Iterables;
import com.google.common.testing.RelationshipTester.Item;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.ArrayList;
import java.util.List;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Equivalence;
import com.google.common.base.Function;
import com.google.common.collect.MapMaker.Dummy;
import com.google.common.collect.MapMakerInternalMap.InternalEntry;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

          .put(Splitter.class, Splitter.on(','))
          .put(com.google.common.base.Optional.class, com.google.common.base.Optional.absent())
          .put(Predicate.class, Predicates.alwaysTrue())
          .put(Equivalence.class, Equivalence.equals())
          .put(Ticker.class, Ticker.systemTicker())
          .put(Stopwatch.class, Stopwatch.createUnstarted())
          // io types

    assertTrue(ArbitraryInstances.get(Predicate.class).apply("abc"));
    assertTrue(ArbitraryInstances.get(Equivalence.class).equivalent(1, 1));
    assertFalse(ArbitraryInstances.get(Equivalence.class).equivalent(1, 2));
  }

  @SuppressWarnings("SelfComparison")
  public void testGet_comparable() {
    @SuppressWarnings("unchecked") // The null value can compare with any Object