/*
    * Copyright (C) 2008 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.testers;
  
  import static com.google.common.collect.testing.features.CollectionFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION;
  import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
  import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
  import static com.google.common.collect.testing.features.CollectionSize.ZERO;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.collect.testing.AbstractCollectionTester;
  import com.google.common.collect.testing.features.CollectionFeature;
  import com.google.common.collect.testing.features.CollectionSize;
  
  import java.util.ConcurrentModificationException;
  import java.util.Iterator;
  
  /**
   * A generic JUnit test which tests {@code clear()} operations on a collection.
   * Can't be invoked directly; please see
   * {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
   *
   * @author George van den Driessche
   */
  @GwtCompatible
  public class CollectionClearTester<E> extends AbstractCollectionTester<E> {
    @CollectionFeature.Require(SUPPORTS_REMOVE)
    public void testClear() {
      collection.clear();
      assertTrue("After clear(), a collection should be empty.",
          collection.isEmpty());
    }
  
    @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
    @CollectionSize.Require(absent = ZERO)
    public void testClear_unsupported() {
      try {
        collection.clear();
        fail("clear() should throw UnsupportedOperation if a collection does "
            + "not support it and is not empty.");
      } catch (UnsupportedOperationException expected) {
      }
      expectUnchanged();
    }
  
    @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
    @CollectionSize.Require(ZERO)
    public void testClear_unsupportedByEmptyCollection() {
      try {
        collection.clear();
      } catch (UnsupportedOperationException tolerated) {
      }
      expectUnchanged();
    }
  
    @CollectionFeature.Require({SUPPORTS_REMOVE,
        FAILS_FAST_ON_CONCURRENT_MODIFICATION})
    @CollectionSize.Require(SEVERAL)
    public void testClearConcurrentWithIteration() {
      try {
        Iterator<E> iterator = collection.iterator();
        collection.clear();
        iterator.next();
        /*
         * We prefer for iterators to fail immediately on hasNext, but ArrayList
         * and LinkedList will notably return true on hasNext here!
         */
        fail("Expected ConcurrentModificationException");
      } catch (ConcurrentModificationException expected) {
        // success
      }
    }
  }