1 /* 2 * Copyright (C) 2007 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.Objects; 26 import com.google.common.collect.ImmutableList; 27 import com.google.common.collect.Iterables; 28 import com.google.common.collect.Lists; 29 import com.google.common.testing.RelationshipTester.RelationshipAssertion; 30 31 import java.util.List; 32 33 /** 34 * Tester for equals() and hashCode() methods of a class. 35 * 36 * <p>To use, create a new EqualsTester and add equality groups where each group 37 * contains objects that are supposed to be equal to each other, and objects of 38 * different groups are expected to be unequal. For example: 39 * <pre> 40 * new EqualsTester() 41 * .addEqualityGroup("hello", "h" + "ello") 42 * .addEqualityGroup("world", "wor" + "ld") 43 * .addEqualityGroup(2, 1 + 1) 44 * .testEquals(); 45 * </pre> 46 * This tests: 47 * <ul> 48 * <li>comparing each object against itself returns true 49 * <li>comparing each object against null returns false 50 * <li>comparing each object an instance of an incompatible class returns false 51 * <li>comparing each pair of objects within the same equality group returns 52 * true 53 * <li>comparing each pair of objects from different equality groups returns 54 * false 55 * <li>the hash code of any two equal objects are equal 56 * </ul> 57 * 58 * <p>When a test fails, the error message labels the objects involved in 59 * the failed comparison as follows: 60 * <ul> 61 * <li>"{@code [group }<i>i</i>{@code , item }<i>j</i>{@code ]}" refers to the 62 * <i>j</i><sup>th</sup> item in the <i>i</i><sup>th</sup> equality group, 63 * where both equality groups and the items within equality groups are 64 * numbered starting from 1. When either a constructor argument or an 65 * equal object is provided, that becomes group 1. 66 * </ul> 67 * 68 * @author Jim McMaster 69 * @author Jige Yu 70 * @since 10.0 71 */ 72 @Beta 73 @GwtCompatible 74 public final class EqualsTester { 75 private static final int REPETITIONS = 3; 76 77 private final List<List<Object>> equalityGroups = Lists.newArrayList(); 78 79 /** 80 * Constructs an empty EqualsTester instance 81 */ 82 public EqualsTester() {} 83 84 /** 85 * Adds {@code equalityGroup} with objects that are supposed to be equal to 86 * each other and not equal to any other equality groups added to this tester. 87 */ 88 public EqualsTester addEqualityGroup(Object... equalityGroup) { 89 checkNotNull(equalityGroup); 90 equalityGroups.add(ImmutableList.copyOf(equalityGroup)); 91 return this; 92 } 93 94 /** 95 * Run tests on equals method, throwing a failure on an invalid test 96 */ 97 public EqualsTester testEquals() { 98 RelationshipTester<Object> delegate = new RelationshipTester<Object>( 99 new RelationshipAssertion<Object>() { 100 @Override public void assertRelated(Object item, Object related) { 101 assertEquals("$ITEM must be equal to $RELATED", item, related); 102 int itemHash = item.hashCode(); 103 int relatedHash = related.hashCode(); 104 assertEquals("the hash (" + itemHash + ") of $ITEM must be equal to the hash (" 105 + relatedHash +") of $RELATED", itemHash, relatedHash); 106 } 107 108 @Override public void assertUnrelated(Object item, Object unrelated) { 109 // TODO(cpovirk): should this implementation (and 110 // RelationshipAssertions in general) accept null inputs? 111 assertTrue("$ITEM must be unequal to $UNRELATED", !Objects.equal(item, unrelated)); 112 } 113 }); 114 for (List<Object> group : equalityGroups) { 115 delegate.addRelatedGroup(group); 116 } 117 for (int run = 0; run < REPETITIONS; run++) { 118 testItems(); 119 delegate.test(); 120 } 121 return this; 122 } 123 124 private void testItems() { 125 for (Object item : Iterables.concat(equalityGroups)) { 126 assertTrue(item + " must be unequal to null", !item.equals(null)); 127 assertTrue(item + " must be unequal to an arbitrary object of another class", 128 !item.equals(NotAnInstance.EQUAL_TO_NOTHING)); 129 assertEquals(item + " must be equal to itself", item, item); 130 assertEquals("the hash of " + item + " must be consistent", item.hashCode(), item.hashCode()); 131 } 132 } 133 134 /** 135 * Class used to test whether equals() correctly handles an instance 136 * of an incompatible class. Since it is a private inner class, the 137 * invoker can never pass in an instance to the tester 138 */ 139 private enum NotAnInstance { 140 EQUAL_TO_NOTHING; 141 } 142 } 143
