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 java.util.List; 29 30 /** 31 * Tester for {@link Equivalence} relationships between groups of objects. 32 * 33 * <p>To use, create a new {@link EquivalenceTester} and add equivalence groups where each group 34 * contains objects that are supposed to be equal to each other. Objects of different groups are 35 * expected to be unequal. For example: 36 * 37 * <pre>{@code 38 * EquivalenceTester.of(someStringEquivalence) 39 * .addEquivalenceGroup("hello", "h" + "ello") 40 * .addEquivalenceGroup("world", "wor" + "ld") 41 * .test(); 42 * }</pre> 43 * 44 * <p>Note that testing {@link Object#equals(Object)} is more simply done using the {@link 45 * EqualsTester}. It includes an extra test against an instance of an arbitrary class without having 46 * to explicitly add another equivalence group. 47 * 48 * @author Gregory Kick 49 * @since 10.0 50 */ 51 @GwtCompatible 52 public final class EquivalenceTester<T> { 53 private static final int REPETITIONS = 3; 54 55 private final Equivalence<? super T> equivalence; 56 private final RelationshipTester<T> delegate; 57 private final List<T> items = Lists.newArrayList(); 58 EquivalenceTester(Equivalence<? super T> equivalence)59 private EquivalenceTester(Equivalence<? super T> equivalence) { 60 this.equivalence = checkNotNull(equivalence); 61 this.delegate = new RelationshipTester<>(equivalence, "equivalent", "hash", new ItemReporter()); 62 } 63 of(Equivalence<? super T> equivalence)64 public static <T> EquivalenceTester<T> of(Equivalence<? super T> equivalence) { 65 return new EquivalenceTester<>(equivalence); 66 } 67 68 /** 69 * Adds a group of objects that are supposed to be equivalent to each other and not equivalent to 70 * objects in any other equivalence group added to this tester. 71 */ addEquivalenceGroup(T first, T... rest)72 public EquivalenceTester<T> addEquivalenceGroup(T first, T... rest) { 73 addEquivalenceGroup(Lists.asList(first, rest)); 74 return this; 75 } 76 addEquivalenceGroup(Iterable<T> group)77 public EquivalenceTester<T> addEquivalenceGroup(Iterable<T> group) { 78 delegate.addRelatedGroup(group); 79 items.addAll(ImmutableList.copyOf(group)); 80 return this; 81 } 82 83 /** Run tests on equivalence methods, throwing a failure on an invalid test */ test()84 public EquivalenceTester<T> test() { 85 for (int run = 0; run < REPETITIONS; run++) { 86 testItems(); 87 delegate.test(); 88 } 89 return this; 90 } 91 testItems()92 private void testItems() { 93 for (T item : items) { 94 /* 95 * TODO(cpovirk): consider no longer running these equivalent() tests on every Equivalence, 96 * since the Equivalence base type now implements this logic itself 97 */ 98 assertTrue(item + " must be inequivalent to null", !equivalence.equivalent(item, null)); 99 assertTrue("null must be inequivalent to " + item, !equivalence.equivalent(null, item)); 100 assertTrue(item + " must be equivalent to itself", equivalence.equivalent(item, item)); 101 assertEquals( 102 "the hash of " + item + " must be consistent", 103 equivalence.hash(item), 104 equivalence.hash(item)); 105 } 106 } 107 } 108