1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
|
/*
* 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>
*
* <p>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>The value you pass to the parameter {@code steps} should be greater than the length of your
* iterator, so that this class can check that your iterator behaves correctly when it is exhausted.
*
* <p>For example, to test {@link java.util.Collections#unmodifiableList(java.util.List)
* Collections.unmodifiableList}'s iterator:
*
* <pre>{@code
* List<String> expectedElements =
* Arrays.asList("a", "b", "c", "d", "e");
* List<String> actualElements =
* Collections.unmodifiableList(
* Arrays.asList("a", "b", "c", "d", "e"));
* IteratorTester<String> iteratorTester =
* new IteratorTester<String>(
* 6,
* IteratorFeature.UNMODIFIABLE,
* expectedElements,
* IteratorTester.KnownOrder.KNOWN_ORDER) {
* @Override
* protected Iterator<String> newTargetIterator() {
* return actualElements.iterator();
* }
* };
* iteratorTester.test();
* iteratorTester.testForEachRemaining();
* }</pre>
*
* <p><b>Note</b>: It is necessary to use {@code IteratorTester.KnownOrder} as shown above, rather
* than {@code KnownOrder} directly, because otherwise the code cannot be compiled.
*
* @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();
}
}
|
