001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.collect.testing.testers;
018
019import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES;
020
021import com.google.common.annotations.GwtCompatible;
022import com.google.common.annotations.GwtIncompatible;
023import com.google.common.collect.testing.Helpers;
024import com.google.common.collect.testing.features.CollectionFeature;
025import com.google.common.collect.testing.features.CollectionSize;
026import java.lang.reflect.Method;
027import java.util.Collection;
028import org.junit.Ignore;
029
030/**
031 * Tests {@link java.util.Set#hashCode}.
032 *
033 * @author George van den Driessche
034 */
035@GwtCompatible(emulated = true)
036@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
037public class SetHashCodeTester<E> extends AbstractSetTester<E> {
038  public void testHashCode() {
039    int expectedHashCode = 0;
040    for (E element : getSampleElements()) {
041      expectedHashCode += ((element == null) ? 0 : element.hashCode());
042    }
043    assertEquals(
044        "A Set's hashCode() should be the sum of those of its elements.",
045        expectedHashCode,
046        getSet().hashCode());
047  }
048
049  @CollectionSize.Require(absent = CollectionSize.ZERO)
050  @CollectionFeature.Require(ALLOWS_NULL_VALUES)
051  public void testHashCode_containingNull() {
052    Collection<E> elements = getSampleElements(getNumElements() - 1);
053    int expectedHashCode = 0;
054    for (E element : elements) {
055      expectedHashCode += ((element == null) ? 0 : element.hashCode());
056    }
057
058    elements.add(null);
059    collection = getSubjectGenerator().create(elements.toArray());
060    assertEquals(
061        "A Set's hashCode() should be the sum of those of its elements (with "
062            + "a null element counting as having a hash of zero).",
063        expectedHashCode,
064        getSet().hashCode());
065  }
066
067  /**
068   * Returns the {@link Method} instances for the test methods in this class which call {@code
069   * hashCode()} on the set values so that set tests on unhashable objects can suppress it with
070   * {@code FeatureSpecificTestSuiteBuilder.suppressing()}.
071   */
072  @GwtIncompatible // reflection
073  public static Method[] getHashCodeMethods() {
074    return new Method[] {
075      Helpers.getMethod(SetHashCodeTester.class, "testHashCode"),
076      Helpers.getMethod(SetHashCodeTester.class, "testHashCode_containingNull")
077    };
078  }
079}