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 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 @Beta
53 @GwtCompatible
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
61 private EquivalenceTester(Equivalence<? super T> equivalence) {
62 this.equivalence = checkNotNull(equivalence);
63 this.delegate =
64 new RelationshipTester<T>(equivalence, "equivalent", "hash", new ItemReporter());
65 }
66
67 public static <T> EquivalenceTester<T> of(Equivalence<? super T> equivalence) {
68 return new EquivalenceTester<T>(equivalence);
69 }
70
71 /**
72 * Adds a group of objects that are supposed to be equivalent to each other and not equivalent to
73 * objects in any other equivalence group added to this tester.
74 */
75 public EquivalenceTester<T> addEquivalenceGroup(T first, T... rest) {
76 addEquivalenceGroup(Lists.asList(first, rest));
77 return this;
78 }
79
80 public EquivalenceTester<T> addEquivalenceGroup(Iterable<T> group) {
81 delegate.addRelatedGroup(group);
82 items.addAll(ImmutableList.copyOf(group));
83 return this;
84 }
85
86 /** Run tests on equivalence methods, throwing a failure on an invalid test */
87 public EquivalenceTester<T> test() {
88 for (int run = 0; run < REPETITIONS; run++) {
89 testItems();
90 delegate.test();
91 }
92 return this;
93 }
94
95 private void testItems() {
96 for (T item : items) {
97 /*
98 * TODO(cpovirk): consider no longer running these equivalent() tests on every Equivalence,
99 * since the Equivalence base type now implements this logic itself
100 */
101 assertTrue(item + " must be inequivalent to null", !equivalence.equivalent(item, null));
102 assertTrue("null must be inequivalent to " + item, !equivalence.equivalent(null, item));
103 assertTrue(item + " must be equivalent to itself", equivalence.equivalent(item, item));
104 assertEquals(
105 "the hash of " + item + " must be consistent",
106 equivalence.hash(item),
107 equivalence.hash(item));
108 }
109 }
110 }