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.Beta; 24 import com.google.common.annotations.GwtCompatible; 25 import com.google.common.base.Equivalence; 26 import com.google.common.collect.ImmutableList; 27 import com.google.common.collect.Lists; 28 import com.google.common.testing.RelationshipTester.ItemReporter; 29 30 import java.util.List; 31 32 /** 33 * Tester for {@link Equivalence} relationships between groups of objects. 34 * 35 * <p> 36 * To use, create a new {@link EquivalenceTester} and add equivalence groups 37 * where each group contains objects that are supposed to be equal to each 38 * other. Objects of different groups are expected to be unequal. For example: 39 * 40 * <pre> 41 * {@code 42 * EquivalenceTester.of(someStringEquivalence) 43 * .addEquivalenceGroup("hello", "h" + "ello") 44 * .addEquivalenceGroup("world", "wor" + "ld") 45 * .test(); 46 * } 47 * </pre> 48 * 49 * <p> 50 * Note that testing {@link Object#equals(Object)} is more simply done using 51 * the {@link EqualsTester}. It includes an extra test against an instance of an 52 * arbitrary class without having to explicitly add another equivalence group. 53 * 54 * @author Gregory Kick 55 * @since 10.0 56 * 57 * TODO(gak): turn this into a test suite so that each test can fail 58 * independently 59 */ 60 @Beta 61 @GwtCompatible public final class EquivalenceTester<T> { 62 private static final int REPETITIONS = 3; 63 64 private final Equivalence<? super T> equivalence; 65 private final RelationshipTester<T> delegate; 66 private final List<T> items = Lists.newArrayList(); 67 EquivalenceTester(Equivalence<? super T> equivalence)68 private EquivalenceTester(Equivalence<? super T> equivalence) { 69 this.equivalence = checkNotNull(equivalence); 70 this.delegate = new RelationshipTester<T>( 71 equivalence, "equivalent", "hash", new ItemReporter()); 72 } 73 of(Equivalence<? super T> equivalence)74 public static <T> EquivalenceTester<T> of(Equivalence<? super T> equivalence) { 75 return new EquivalenceTester<T>(equivalence); 76 } 77 78 /** 79 * Adds a group of objects that are supposed to be equivalent to each other 80 * and not equivalent to objects in any other equivalence group added to this 81 * tester. 82 */ addEquivalenceGroup(T first, T... rest)83 public EquivalenceTester<T> addEquivalenceGroup(T first, T... rest) { 84 addEquivalenceGroup(Lists.asList(first, rest)); 85 return this; 86 } 87 addEquivalenceGroup(Iterable<T> group)88 public EquivalenceTester<T> addEquivalenceGroup(Iterable<T> group) { 89 delegate.addRelatedGroup(group); 90 items.addAll(ImmutableList.copyOf(group)); 91 return this; 92 } 93 94 /** Run tests on equivalence methods, throwing a failure on an invalid test */ test()95 public EquivalenceTester<T> test() { 96 for (int run = 0; run < REPETITIONS; run++) { 97 testItems(); 98 delegate.test(); 99 } 100 return this; 101 } 102 testItems()103 private void testItems() { 104 for (T item : items) { 105 /* 106 * TODO(cpovirk): consider no longer running these equivalent() tests on every Equivalence, 107 * since the Equivalence base type now implements this logic itself 108 */ 109 assertTrue(item + " must be inequivalent to null", !equivalence.equivalent(item, null)); 110 assertTrue("null must be inequivalent to " + item, !equivalence.equivalent(null, item)); 111 assertTrue(item + " must be equivalent to itself", equivalence.equivalent(item, item)); 112 assertEquals("the hash of " + item + " must be consistent", equivalence.hash(item), 113 equivalence.hash(item)); 114 } 115 } 116 } 117