001/*
002 * Copyright (C) 2007 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;
018
019import com.google.common.annotations.GwtCompatible;
020import java.util.Collection;
021
022/**
023 * Base class for collection testers.
024 *
025 * @param <E> the element type of the collection to be tested.
026 * @author Kevin Bourrillion
027 */
028@GwtCompatible
029public abstract class AbstractCollectionTester<E>
030    extends AbstractContainerTester<Collection<E>, E> {
031
032  // TODO: replace this with an accessor.
033  protected Collection<E> collection;
034
035  @Override
036  protected Collection<E> actualContents() {
037    return collection;
038  }
039
040  // TODO: dispose of this once collection is encapsulated.
041  @Override
042  protected Collection<E> resetContainer(Collection<E> newContents) {
043    collection = super.resetContainer(newContents);
044    return collection;
045  }
046
047  /** @see AbstractContainerTester#resetContainer() */
048  protected void resetCollection() {
049    resetContainer();
050  }
051
052  /** @return an array of the proper size with {@code null} inserted into the middle element. */
053  protected E[] createArrayWithNullElement() {
054    E[] array = createSamplesArray();
055    array[getNullLocation()] = null;
056    return array;
057  }
058
059  protected void initCollectionWithNullElement() {
060    E[] array = createArrayWithNullElement();
061    resetContainer(getSubjectGenerator().create(array));
062  }
063
064  /**
065   * Equivalent to {@link #expectMissing(Object[]) expectMissing}{@code (null)} except that the call
066   * to {@code contains(null)} is permitted to throw a {@code NullPointerException}.
067   *
068   * @param message message to use upon assertion failure
069   */
070  protected void expectNullMissingWhenNullUnsupported(String message) {
071    try {
072      assertFalse(message, actualContents().contains(null));
073    } catch (NullPointerException tolerated) {
074      // Tolerated
075    }
076  }
077}