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