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/*
* 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.Collections;
import java.util.Iterator;
/**
* A utility for testing an Iterator implementation by comparing its behavior to
* that of a "known good" reference implementation. In order to accomplish this,
* it's important to test a great variety of sequences of the
* {@link Iterator#next}, {@link Iterator#hasNext} and {@link Iterator#remove}
* operations. This utility takes the brute-force approach of trying <i>all</i>
* possible sequences of these operations, up to a given number of steps. So, if
* the caller specifies to use <i>n</i> steps, a total of <i>3^n</i> tests are
* actually performed.
*
* <p>For instance, if <i>steps</i> is 5, one example sequence that will be
* tested is:
*
* <ol>
* <li>remove();
* <li>hasNext()
* <li>hasNext();
* <li>remove();
* <li>next();
* </ol>
*
* This particular order of operations may be unrealistic, and testing all 3^5
* of them may be thought of as overkill; however, it's difficult to determine
* which proper subset of this massive set would be sufficient to expose any
* possible bug. Brute force is simpler.
*
* <p>To use this class the concrete subclass must implement the
* {@link IteratorTester#newTargetIterator()} method. This is because it's
* impossible to test an Iterator without changing its state, so the tester
* needs a steady supply of fresh Iterators.
*
* <p>If your iterator supports modification through {@code remove()}, you may
* wish to override the verify() method, which is called <em>after</em>
* each sequence and is guaranteed to be called using the latest values
* obtained from {@link IteratorTester#newTargetIterator()}.
*
* <p>This class is GWT compatible.
*
* @author Kevin Bourrillion
* @author Chris Povirk
*/
@GwtCompatible
public abstract class IteratorTester<E> extends
AbstractIteratorTester<E, Iterator<E>> {
/**
* Creates an IteratorTester.
*
* @param steps how many operations to test for each tested pair of iterators
* @param features the features supported by the iterator
*/
protected IteratorTester(int steps,
Iterable<? extends IteratorFeature> features,
Iterable<E> expectedElements, KnownOrder knownOrder) {
super(steps, Collections.<E>singleton(null), features, expectedElements,
knownOrder, 0);
}
@Override
protected final Iterable<Stimulus<E, Iterator<E>>> getStimulusValues() {
return iteratorStimuli();
}
}
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