/**
* Copyright 2008 Google Inc.
*
* 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 org.waveprotocol.wave.model.util;
import static java.util.Arrays.asList;
import junit.framework.TestCase;
import java.util.ArrayList;
import java.util.Collections;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
/**
* Test case for {@link ConcurrentList}.
*
*/
public class ConcurrentListTest extends TestCase {
/** Instance being tested. Created in {@link #setUp()}. */
private ConcurrentList<String> list;
/** Dummy items used in the tests. */
private String a;
private String b;
private String c;
private String d;
private String e;
@Override
protected void setUp() throws Exception {
list = ConcurrentList.create();
a = "a";
b = "b";
c = "c";
d = "d";
e = "e";
}
/**
* Creates a list of items in the order returned by iterating over a
* ConcurrentList.
*
* @param xs a ConcurrentList
* @return a list containing the items returned by iterating over {@code xs}.
*/
private static <T> List<T> toList(ConcurrentList<T> xs) {
List<T> list = new ArrayList<T>();
for (T x : xs) {
list.add(x);
}
return list;
}
public void testBasicAddAndRemove() {
assertTrue(list.isEmpty());
list.add(a);
assertEquals("initial add failed", asList(a), toList(list));
assertTrue(!list.isEmpty());
list.add(b);
assertEquals("second add failed", asList(b, a), toList(list));
assertTrue(!list.isEmpty());
list.remove(a);
assertEquals("initial remove failed", asList(b), toList(list));
assertTrue(!list.isEmpty());
list.remove(b);
assertEquals("second remove failed", Collections.<String>emptyList(), toList(list));
assertTrue(list.isEmpty());
}
public void testAddWhileIteratingDoesNotCauseCme() {
list.add(a);
list.add(b);
list.add(c);
try {
// We attempt to add d on every iteration.
for (String x : list) {
list.add(d);
}
} catch (ConcurrentModificationException e) {
fail("addition during iteration caused CME");
}
}
public void testRemoveWhileIteratingDoesNotCauseCme() {
list.add(d);
list.add(c);
list.add(b);
list.add(a);
try {
Iterator<String> i = list.iterator();
// (* means iterator reference, [] means deleted
// pre state: a* b c d
assertTrue(i.hasNext());
assertEquals(a, i.next());
// post state: a b* c d
// pre state: a b* c d
list.remove(c);
assertEquals(asList(a, b, d), toList(list));
// post state: a b* d
// pre state: a b* d
assertTrue(i.hasNext());
assertEquals(b, i.next());
// post state: a b d*
// pre state: a b d*
list.remove(d);
assertEquals(asList(a, b), toList(list));
// post state: a b [d*]
assertFalse(i.hasNext());
} catch (ConcurrentModificationException e) {
fail("removal during iteration caused CME");
}
}
public void testAddAndRemoveWhileIterating() {
list.add(e);
list.add(d);
list.add(c);
list.add(b);
list.add(a);
try {
Iterator<String> i = list.iterator();
//
// pre state: a* b c d e
assertTrue(i.hasNext());
assertEquals(a, i.next());
// post state: a b* c d e
// pre state: a b* c d e
list.remove(e);
list.add(e);
assertEquals(asList(e, a, b, c, d), toList(list));
// post state: e a b* c d
// pre state: e a b* c d
assertTrue(i.hasNext());
list.remove(b);
assertEquals(asList(e, a, c, d), toList(list));
// post state: e a [b*] c d
list.remove(c);
assertEquals(asList(e, a, d), toList(list));
// post state: e a [b*] [c] d
assertTrue(i.hasNext());
assertEquals(d, i.next());
// post state: e a d
assertFalse(i.hasNext());
} catch (ConcurrentModificationException e) {
fail("mutation during iteration caused CME");
}
}
public void testHasNextDoesNotAffectNext() {
list.add(d);
list.add(c);
list.add(b);
list.add(a);
try {
Iterator<String> i = list.iterator();
assertTrue(i.hasNext());
assertTrue(i.hasNext());
assertTrue(i.hasNext());
assertEquals(a, i.next());
list.remove(b);
assertTrue(i.hasNext());
assertTrue(i.hasNext());
assertTrue(i.hasNext());
assertEquals(c, i.next());
assertTrue(i.hasNext());
assertTrue(i.hasNext());
assertTrue(i.hasNext());
assertEquals(d, i.next());
assertFalse(i.hasNext());
assertFalse(i.hasNext());
assertFalse(i.hasNext());
} catch (ConcurrentModificationException e) {
fail("mutation during iteration caused CME");
}
}
public void testNextMatchesHasNext() {
list.add(d);
list.add(c);
list.add(b);
list.add(a);
try {
Iterator<String> i = list.iterator();
// Even if we remove stuff, we expect next() to return what was pointed to at the time
// of hasNext().
// pre state: a* b c d
assertTrue(i.hasNext()); // a
list.remove(a);
assertEquals(a, i.next());
// post state: b* c d
assertTrue(i.hasNext()); // b
list.remove(b);
list.remove(c);
assertEquals(b, i.next());
// post state: d*
assertTrue(i.hasNext()); // d
assertEquals(d, i.next()); // d
} catch (ConcurrentModificationException e) {
fail("mutation during iteration caused CME");
}
}
public void testRemoveWhileIteratingAffectsIsEmpty() {
list.add(c);
list.add(b);
list.add(a);
try {
Iterator<String> i = list.iterator();
assertFalse(list.isEmpty());
// pre state: a* b c
list.remove(c);
i.next();
assertFalse(list.isEmpty());
// post state: a b*
// pre state: a b*
list.remove(b);
list.remove(a);
assertEquals(Collections.<String>emptyList(), toList(list));
assertFalse(i.hasNext());
assertTrue(list.isEmpty());
// post state: [b*]
} catch (ConcurrentModificationException e) {
fail("removal during iteration caused CME");
}
}
}