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.annotations.J2ktIncompatible;
024import com.google.common.collect.testing.Helpers;
025import com.google.common.collect.testing.features.CollectionFeature;
026import com.google.common.collect.testing.features.CollectionSize;
027import java.lang.reflect.Method;
028import java.util.Collection;
029import org.junit.Ignore;
030
031/**
032 * Tests {@link java.util.Set#hashCode}.
033 *
034 * @author George van den Driessche
035 */
036@GwtCompatible(emulated = true)
037@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
038public class SetHashCodeTester<E> extends AbstractSetTester<E> {
039  public void testHashCode() {
040    int expectedHashCode = 0;
041    for (E element : getSampleElements()) {
042      expectedHashCode += ((element == null) ? 0 : element.hashCode());
043    }
044    assertEquals(
045        "A Set's hashCode() should be the sum of those of its elements.",
046        expectedHashCode,
047        getSet().hashCode());
048  }
049
050  @CollectionSize.Require(absent = CollectionSize.ZERO)
051  @CollectionFeature.Require(ALLOWS_NULL_VALUES)
052  public void testHashCode_containingNull() {
053    Collection<E> elements = getSampleElements(getNumElements() - 1);
054    int expectedHashCode = 0;
055    for (E element : elements) {
056      expectedHashCode += ((element == null) ? 0 : element.hashCode());
057    }
058
059    elements.add(null);
060    collection = getSubjectGenerator().create(elements.toArray());
061    assertEquals(
062        "A Set's hashCode() should be the sum of those of its elements (with "
063            + "a null element counting as having a hash of zero).",
064        expectedHashCode,
065        getSet().hashCode());
066  }
067
068  /**
069   * Returns the {@link Method} instances for the test methods in this class which call {@code
070   * hashCode()} on the set values so that set tests on unhashable objects can suppress it with
071   * {@code FeatureSpecificTestSuiteBuilder.suppressing()}.
072   */
073  @J2ktIncompatible
074  @GwtIncompatible // reflection
075  public static Method[] getHashCodeMethods() {
076    return new Method[] {
077      Helpers.getMethod(SetHashCodeTester.class, "testHashCode"),
078      Helpers.getMethod(SetHashCodeTester.class, "testHashCode_containingNull")
079    };
080  }
081}