/*
* Copyright (C) 2011 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.testing;
import static com.google.common.base.Preconditions.checkNotNull;
import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertTrue;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Equivalence;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.testing.RelationshipTester.ItemReporter;
import java.util.List;
/**
* Tester for {@link Equivalence} relationships between groups of objects.
*
* <p>
* To use, create a new {@link EquivalenceTester} and add equivalence groups
* where each group contains objects that are supposed to be equal to each
* other. Objects of different groups are expected to be unequal. For example:
*
* <pre>
* {@code
* EquivalenceTester.of(someStringEquivalence)
* .addEquivalenceGroup("hello", "h" + "ello")
* .addEquivalenceGroup("world", "wor" + "ld")
* .test();
* }
* </pre>
*
* <p>
* Note that testing {@link Object#equals(Object)} is more simply done using
* the {@link EqualsTester}. It includes an extra test against an instance of an
* arbitrary class without having to explicitly add another equivalence group.
*
* @author Gregory Kick
* @since 10.0
*
* TODO(gak): turn this into a test suite so that each test can fail
* independently
*/
@Beta
@GwtCompatible public final class EquivalenceTester<T> {
private static final int REPETITIONS = 3;
private final Equivalence<? super T> equivalence;
private final RelationshipTester<T> delegate;
private final List<T> items = Lists.newArrayList();
private EquivalenceTester(Equivalence<? super T> equivalence) {
this.equivalence = checkNotNull(equivalence);
this.delegate = new RelationshipTester<T>(
equivalence, "equivalent", "hash", new ItemReporter());
}
public static <T> EquivalenceTester<T> of(Equivalence<? super T> equivalence) {
return new EquivalenceTester<T>(equivalence);
}
/**
* Adds a group of objects that are supposed to be equivalent to each other
* and not equivalent to objects in any other equivalence group added to this
* tester.
*/
public EquivalenceTester<T> addEquivalenceGroup(T first, T... rest) {
addEquivalenceGroup(Lists.asList(first, rest));
return this;
}
public EquivalenceTester<T> addEquivalenceGroup(Iterable<T> group) {
delegate.addRelatedGroup(group);
items.addAll(ImmutableList.copyOf(group));
return this;
}
/** Run tests on equivalence methods, throwing a failure on an invalid test */
public EquivalenceTester<T> test() {
for (int run = 0; run < REPETITIONS; run++) {
testItems();
delegate.test();
}
return this;
}
private void testItems() {
for (T item : items) {
/*
* TODO(cpovirk): consider no longer running these equivalent() tests on every Equivalence,
* since the Equivalence base type now implements this logic itself
*/
assertTrue(item + " must be inequivalent to null", !equivalence.equivalent(item, null));
assertTrue("null must be inequivalent to " + item, !equivalence.equivalent(null, item));
assertTrue(item + " must be equivalent to itself", equivalence.equivalent(item, item));
assertEquals("the hash of " + item + " must be consistent", equivalence.hash(item),
equivalence.hash(item));
}
}
}