1 /* 2 * Copyright (C) 2011 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.testing; 18 19 import static com.google.common.base.Preconditions.checkNotNull; 20 import static junit.framework.Assert.assertEquals; 21 import static junit.framework.Assert.assertTrue; 22 23 import com.google.common.annotations.GwtCompatible; 24 import com.google.common.base.Equivalence; 25 import com.google.common.collect.ImmutableList; 26 import com.google.common.collect.Lists; 27 import com.google.common.testing.RelationshipTester.ItemReporter; 28 import com.google.errorprone.annotations.CanIgnoreReturnValue; 29 import java.util.List; 30 31 /** 32 * Tester for {@link Equivalence} relationships between groups of objects. 33 * 34 * <p>To use, create a new {@link EquivalenceTester} and add equivalence groups where each group 35 * contains objects that are supposed to be equal to each other. Objects of different groups are 36 * expected to be unequal. For example: 37 * 38 * <pre>{@code 39 * EquivalenceTester.of(someStringEquivalence) 40 * .addEquivalenceGroup("hello", "h" + "ello") 41 * .addEquivalenceGroup("world", "wor" + "ld") 42 * .test(); 43 * }</pre> 44 * 45 * <p>Note that testing {@link Object#equals(Object)} is more simply done using the {@link 46 * EqualsTester}. It includes an extra test against an instance of an arbitrary class without having 47 * to explicitly add another equivalence group. 48 * 49 * @author Gregory Kick 50 * @since 10.0 51 */ 52 @GwtCompatible 53 @ElementTypesAreNonnullByDefault 54 public final class EquivalenceTester<T> { 55 private static final int REPETITIONS = 3; 56 57 private final Equivalence<? super T> equivalence; 58 private final RelationshipTester<T> delegate; 59 private final List<T> items = Lists.newArrayList(); 60 EquivalenceTester(Equivalence<? super T> equivalence)61 private EquivalenceTester(Equivalence<? super T> equivalence) { 62 this.equivalence = checkNotNull(equivalence); 63 this.delegate = new RelationshipTester<>(equivalence, "equivalent", "hash", new ItemReporter()); 64 } 65 of(Equivalence<? super T> equivalence)66 public static <T> EquivalenceTester<T> of(Equivalence<? super T> equivalence) { 67 return new EquivalenceTester<>(equivalence); 68 } 69 70 /** 71 * Adds a group of objects that are supposed to be equivalent to each other and not equivalent to 72 * objects in any other equivalence group added to this tester. 73 */ 74 @CanIgnoreReturnValue addEquivalenceGroup(T first, T... rest)75 public EquivalenceTester<T> addEquivalenceGroup(T first, T... rest) { 76 addEquivalenceGroup(Lists.asList(first, rest)); 77 return this; 78 } 79 80 @CanIgnoreReturnValue addEquivalenceGroup(Iterable<T> group)81 public EquivalenceTester<T> addEquivalenceGroup(Iterable<T> group) { 82 delegate.addRelatedGroup(group); 83 items.addAll(ImmutableList.copyOf(group)); 84 return this; 85 } 86 87 /** Run tests on equivalence methods, throwing a failure on an invalid test */ 88 @CanIgnoreReturnValue test()89 public EquivalenceTester<T> test() { 90 for (int run = 0; run < REPETITIONS; run++) { 91 testItems(); 92 delegate.test(); 93 } 94 return this; 95 } 96 testItems()97 private void testItems() { 98 for (T item : items) { 99 /* 100 * TODO(cpovirk): consider no longer running these equivalent() tests on every Equivalence, 101 * since the Equivalence base type now implements this logic itself 102 */ 103 assertTrue(item + " must be inequivalent to null", !equivalence.equivalent(item, null)); 104 assertTrue("null must be inequivalent to " + item, !equivalence.equivalent(null, item)); 105 assertTrue(item + " must be equivalent to itself", equivalence.equivalent(item, item)); 106 assertEquals( 107 "the hash of " + item + " must be consistent", 108 equivalence.hash(item), 109 equivalence.hash(item)); 110 } 111 } 112 } 113