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 com.google.common.annotations.GwtCompatible;
020import com.google.common.annotations.GwtIncompatible;
021import com.google.common.annotations.J2ktIncompatible;
022import com.google.common.collect.testing.Helpers;
023import java.lang.reflect.Method;
024import org.junit.Ignore;
025
026/**
027 * Tests {@link java.util.List#hashCode}.
028 *
029 * @author George van den Driessche
030 */
031@GwtCompatible(emulated = true)
032@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
033public class ListHashCodeTester<E> extends AbstractListTester<E> {
034  public void testHashCode() {
035    int expectedHashCode = 1;
036    for (E element : getOrderedElements()) {
037      expectedHashCode = 31 * expectedHashCode + ((element == null) ? 0 : element.hashCode());
038    }
039    assertEquals(
040        "A List's hashCode() should be computed from those of its elements.",
041        expectedHashCode,
042        getList().hashCode());
043  }
044
045  /**
046   * Returns the {@link Method} instance for {@link #testHashCode()} so that list tests on
047   * unhashable objects can suppress it with {@code FeatureSpecificTestSuiteBuilder.suppressing()}.
048   */
049  @J2ktIncompatible
050  @GwtIncompatible // reflection
051  public static Method getHashCodeMethod() {
052    return Helpers.getMethod(ListHashCodeTester.class, "testHashCode");
053  }
054}