1 /* 2 * Copyright (C) 2008 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.collect.testing.testers; 18 19 import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES; 20 21 import com.google.common.annotations.GwtCompatible; 22 import com.google.common.annotations.GwtIncompatible; 23 import com.google.common.collect.testing.Helpers; 24 import com.google.common.collect.testing.features.CollectionFeature; 25 import com.google.common.collect.testing.features.CollectionSize; 26 27 import java.lang.reflect.Method; 28 import java.util.Collection; 29 30 /** 31 * Tests {@link java.util.Set#hashCode}. 32 * 33 * @author George van den Driessche 34 */ 35 @GwtCompatible(emulated = true) 36 public class SetHashCodeTester<E> extends AbstractSetTester<E> { testHashCode()37 public void testHashCode() { 38 int expectedHashCode = 0; 39 for (E element : getSampleElements()) { 40 expectedHashCode += ((element == null) ? 0 : element.hashCode()); 41 } 42 assertEquals( 43 "A Set's hashCode() should be the sum of those of its elements.", 44 expectedHashCode, getSet().hashCode()); 45 } 46 47 @CollectionSize.Require(absent = CollectionSize.ZERO) 48 @CollectionFeature.Require(ALLOWS_NULL_VALUES) testHashCode_containingNull()49 public void testHashCode_containingNull() { 50 Collection<E> elements = getSampleElements(getNumElements() - 1); 51 int expectedHashCode = 0; 52 for (E element : elements) { 53 expectedHashCode += ((element == null) ? 0 : element.hashCode()); 54 } 55 56 elements.add(null); 57 collection = getSubjectGenerator().create(elements.toArray()); 58 assertEquals( 59 "A Set's hashCode() should be the sum of those of its elements (with " 60 + "a null element counting as having a hash of zero).", 61 expectedHashCode, getSet().hashCode()); 62 } 63 64 /** 65 * Returns the {@link Method} instances for the test methods in this class 66 * which call {@code hashCode()} on the set values so that set tests on 67 * unhashable objects can suppress it with 68 * {@code FeatureSpecificTestSuiteBuilder.suppressing()}. 69 */ 70 @GwtIncompatible("reflection") getHashCodeMethods()71 public static Method[] getHashCodeMethods() { 72 return new Method[]{ 73 Helpers.getMethod(SetHashCodeTester.class, "testHashCode"), 74 Helpers.getMethod(SetHashCodeTester.class, "testHashCode_containingNull") }; 75 } 76 } 77