/*
    * Copyright (C) 2007 The Guava Authors
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.google.common.collect.testing;
  
  import com.google.common.annotations.GwtCompatible;
  
  import java.util.Collection;
  
  /**
   * Base class for collection testers.
   *
   * @param <E> the element type of the collection to be tested.
   *
   * @author Kevin Bourrillion
   */
  @GwtCompatible
  public abstract class AbstractCollectionTester<E>
      extends AbstractContainerTester<Collection<E>, E> {
  
    // TODO: replace this with an accessor.
    protected Collection<E> collection;
  
    @Override protected Collection<E> actualContents() {
      return collection;
    }
  
    // TODO: dispose of this once collection is encapsulated.
    @Override protected Collection<E> resetContainer(Collection<E> newContents) {
      collection = super.resetContainer(newContents);
      return collection;
    }
  
    /** @see AbstractContainerTester#resetContainer() */
    protected void resetCollection() {
      resetContainer();
    }
  
    /**
     * @return an array of the proper size with {@code null} inserted into the
     * middle element.
     */
    protected E[] createArrayWithNullElement() {
      E[] array = createSamplesArray();
      array[getNullLocation()] = null;
      return array;
    }
  
    protected void initCollectionWithNullElement() {
      E[] array = createArrayWithNullElement();
      resetContainer(getSubjectGenerator().create(array));
    }
  
    /**
     * Equivalent to {@link #expectMissing(Object[]) expectMissing}{@code (null)}
     * except that the call to {@code contains(null)} is permitted to throw a
     * {@code NullPointerException}.
     *
     * @param message message to use upon assertion failure
     */
    protected void expectNullMissingWhenNullUnsupported(String message) {
      try {
        assertFalse(message, actualContents().contains(null));
      } catch (NullPointerException tolerated) {
        // Tolerated
      }
    }
  }