guava

1
/*
2
 * Copyright (C) 2008 The Guava Authors
3
 *
4
 * Licensed under the Apache License, Version 2.0 (the "License");
5
 * you may not use this file except in compliance with the License.
6
 * You may obtain a copy of the License at
7
 *
8
 * http://www.apache.org/licenses/LICENSE-2.0
9
 *
10
 * Unless required by applicable law or agreed to in writing, software
11
 * distributed under the License is distributed on an "AS IS" BASIS,
12
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13
 * See the License for the specific language governing permissions and
14
 * limitations under the License.
15
 */
16

17
package com.google.common.collect.testing.testers;
18

19
import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES;
20

21
import com.google.common.annotations.GwtCompatible;
22
import com.google.common.annotations.GwtIncompatible;
23
import com.google.common.annotations.J2ktIncompatible;
24
import com.google.common.collect.testing.Helpers;
25
import com.google.common.collect.testing.features.CollectionFeature;
26
import com.google.common.collect.testing.features.CollectionSize;
27
import java.lang.reflect.Method;
28
import java.util.Collection;
29
import org.junit.Ignore;
30

31
/**
32
 * Tests {@link java.util.Set#hashCode}.
33
 *
34
 * @author George van den Driessche
35
 */
36
@GwtCompatible(emulated = true)
37
@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
38
public class SetHashCodeTester<E> extends AbstractSetTester<E> {
39
  public void testHashCode() {
40
    int expectedHashCode = 0;
41
    for (E element : getSampleElements()) {
42
      expectedHashCode += ((element == null) ? 0 : element.hashCode());
43
    }
44
    assertEquals(
45
        "A Set's hashCode() should be the sum of those of its elements.",
46
        expectedHashCode,
47
        getSet().hashCode());
48
  }
49

50
  @CollectionSize.Require(absent = CollectionSize.ZERO)
51
  @CollectionFeature.Require(ALLOWS_NULL_VALUES)
52
  public void testHashCode_containingNull() {
53
    Collection<E> elements = getSampleElements(getNumElements() - 1);
54
    int expectedHashCode = 0;
55
    for (E element : elements) {
56
      expectedHashCode += ((element == null) ? 0 : element.hashCode());
57
    }
58

59
    elements.add(null);
60
    collection = getSubjectGenerator().create(elements.toArray());
61
    assertEquals(
62
        "A Set's hashCode() should be the sum of those of its elements (with "
63
            + "a null element counting as having a hash of zero).",
64
        expectedHashCode,
65
        getSet().hashCode());
66
  }
67

68
  /**
69
   * Returns the {@link Method} instances for the test methods in this class which call {@code
70
   * hashCode()} on the set values so that set tests on unhashable objects can suppress it with
71
   * {@code FeatureSpecificTestSuiteBuilder.suppressing()}.
72
   */
73
  @J2ktIncompatible
74
  @GwtIncompatible // reflection
75
  public static Method[] getHashCodeMethods() {
76
    return new Method[] {
77
      Helpers.getMethod(SetHashCodeTester.class, "testHashCode"),
78
      Helpers.getMethod(SetHashCodeTester.class, "testHashCode_containingNull")
79
    };
80
  }
81
}
82