test/tck/Collection8Test.java

/*
 * Written by Doug Lea and Martin Buchholz with assistance from
 * members of JCP JSR-166 Expert Group and released to the public
 * domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

import static java.util.concurrent.TimeUnit.MILLISECONDS;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Deque;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Queue;
import java.util.Spliterator;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;
import java.util.function.Predicate;

import junit.framework.Test;

/**
 * Contains tests applicable to all jdk8+ Collection implementations.
 * An extension of CollectionTest.
 */
public class Collection8Test extends JSR166TestCase {
    final CollectionImplementation impl;

    /** Tests are parameterized by a Collection implementation. */
    Collection8Test(CollectionImplementation impl, String methodName) {
        super(methodName);
        this.impl = impl;
    }

    public static Test testSuite(CollectionImplementation impl) {
        return parameterizedTestSuite(Collection8Test.class,
                                      CollectionImplementation.class,
                                      impl);
    }

    /** Checks properties of empty collections. */
    public void testEmptyMeansEmpty() {
        Collection c = impl.emptyCollection();
        assertTrue(c.isEmpty());
        assertEquals(0, c.size());
        assertEquals("[]", c.toString());
        {
            Object[] a = c.toArray();
            assertEquals(0, a.length);
            assertSame(Object[].class, a.getClass());
        }
        {
            Object[] a = new Object[0];
            assertSame(a, c.toArray(a));
        }
        {
            Integer[] a = new Integer[0];
            assertSame(a, c.toArray(a));
        }
        {
            Integer[] a = { 1, 2, 3};
            assertSame(a, c.toArray(a));
            assertNull(a[0]);
            assertSame(2, a[1]);
            assertSame(3, a[2]);
        }
        assertIteratorExhausted(c.iterator());
        Consumer alwaysThrows = (e) -> { throw new AssertionError(); };
        c.forEach(alwaysThrows);
        c.iterator().forEachRemaining(alwaysThrows);
        c.spliterator().forEachRemaining(alwaysThrows);
        assertFalse(c.spliterator().tryAdvance(alwaysThrows));
        if (Queue.class.isAssignableFrom(impl.klazz())) {
            Queue q = (Queue) c;
            assertNull(q.peek());
            assertNull(q.poll());
        }
        if (Deque.class.isAssignableFrom(impl.klazz())) {
            Deque d = (Deque) c;
            assertNull(d.peekFirst());
            assertNull(d.peekLast());
            assertNull(d.pollFirst());
            assertNull(d.pollLast());
            assertIteratorExhausted(d.descendingIterator());
        }
    }

    public void testNullPointerExceptions() {
        Collection c = impl.emptyCollection();
        assertThrows(
            NullPointerException.class,
            () -> c.addAll(null),
            () -> c.containsAll(null),
            () -> c.retainAll(null),
            () -> c.removeAll(null),
            () -> c.removeIf(null),
            () -> c.toArray(null));

        if (!impl.permitsNulls()) {
            assertThrows(
                NullPointerException.class,
                () -> c.add(null));
        }
        if (!impl.permitsNulls()
            && Queue.class.isAssignableFrom(impl.klazz())) {
            Queue q = (Queue) c;
            assertThrows(
                NullPointerException.class,
                () -> q.offer(null));
        }
        if (!impl.permitsNulls()
            && Deque.class.isAssignableFrom(impl.klazz())) {
            Deque d = (Deque) c;
            assertThrows(
                NullPointerException.class,
                () -> d.addFirst(null),
                () -> d.addLast(null),
                () -> d.offerFirst(null),
                () -> d.offerLast(null),
                () -> d.push(null));
        }
    }

    public void testNoSuchElementExceptions() {
        Collection c = impl.emptyCollection();
        assertThrows(
            NoSuchElementException.class,
            () -> c.iterator().next());

        if (Queue.class.isAssignableFrom(impl.klazz())) {
            Queue q = (Queue) c;
            assertThrows(
                NoSuchElementException.class,
                () -> q.element(),
                () -> q.remove());
        }
        if (Deque.class.isAssignableFrom(impl.klazz())) {
            Deque d = (Deque) c;
            assertThrows(
                NoSuchElementException.class,
                () -> d.getFirst(),
                () -> d.getLast(),
                () -> d.removeFirst(),
                () -> d.removeLast(),
                () -> d.pop(),
                () -> d.descendingIterator().next());
        }
    }

    public void testRemoveIf() {
        Collection c = impl.emptyCollection();
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        int n = rnd.nextInt(6);
        for (int i = 0; i < n; i++) c.add(impl.makeElement(i));
        AtomicReference threwAt = new AtomicReference(null);
        ArrayList survivors = new ArrayList(c);
        ArrayList accepts = new ArrayList();
        ArrayList rejects = new ArrayList();
        Predicate randomPredicate = (e) -> {
            assertNull(threwAt.get());
            switch (rnd.nextInt(3)) {
            case 0: accepts.add(e); return true;
            case 1: rejects.add(e); return false;
            case 2: threwAt.set(e); throw new ArithmeticException();
            default: throw new AssertionError();
            }
        };
        try {
            boolean modified = c.removeIf(randomPredicate);
            if (!modified) {
                assertNull(threwAt.get());
                assertEquals(n, rejects.size());
                assertEquals(0, accepts.size());
            }
        } catch (ArithmeticException ok) {}
        survivors.removeAll(accepts);
        if (n - accepts.size() != c.size()) {
            System.err.println(impl.klazz());
            System.err.println(c);
            System.err.println(accepts);
            System.err.println(rejects);
            System.err.println(survivors);
            System.err.println(threwAt.get());
        }
        assertEquals(n - accepts.size(), c.size());
        assertTrue(c.containsAll(survivors));
        assertTrue(survivors.containsAll(rejects));
        for (Object x : accepts) assertFalse(c.contains(x));
        if (threwAt.get() == null)
            assertEquals(accepts.size() + rejects.size(), n);
    }

    /**
     * Various ways of traversing a collection yield same elements
     */
    public void testIteratorEquivalence() {
        Collection c = impl.emptyCollection();
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        int n = rnd.nextInt(6);
        for (int i = 0; i < n; i++) c.add(impl.makeElement(i));
        ArrayList iterated = new ArrayList();
        ArrayList iteratedForEachRemaining = new ArrayList();
        ArrayList spliterated = new ArrayList();
        ArrayList foreached = new ArrayList();
        for (Object x : c) iterated.add(x);
        c.iterator().forEachRemaining(e -> iteratedForEachRemaining.add(e));
        c.spliterator().forEachRemaining(e -> spliterated.add(e));
        c.forEach(e -> foreached.add(e));
        boolean ordered =
            c.spliterator().hasCharacteristics(Spliterator.ORDERED);
        if (c instanceof List || c instanceof Deque)
            assertTrue(ordered);
        if (ordered) {
            assertEquals(iterated, iteratedForEachRemaining);
            assertEquals(iterated, spliterated);
            assertEquals(iterated, foreached);
        } else {
            HashSet cset = new HashSet(c);
            assertEquals(cset, new HashSet(iterated));
            assertEquals(cset, new HashSet(iteratedForEachRemaining));
            assertEquals(cset, new HashSet(spliterated));
            assertEquals(cset, new HashSet(foreached));
        }
        if (c instanceof Deque) {
            Deque d = (Deque) c;
            ArrayList descending = new ArrayList();
            ArrayList descendingForEachRemaining = new ArrayList();
            for (Iterator it = d.descendingIterator(); it.hasNext(); )
                descending.add(it.next());
            d.descendingIterator().forEachRemaining(
                e -> descendingForEachRemaining.add(e));
            Collections.reverse(descending);
            Collections.reverse(descendingForEachRemaining);
            assertEquals(iterated, descending);
            assertEquals(iterated, descendingForEachRemaining);
        }
    }

    /**
     * Calling Iterator#remove() after Iterator#forEachRemaining
     * should remove last element
     */
    public void testRemoveAfterForEachRemaining() {
        Collection c = impl.emptyCollection();
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        {
            int n = 3 + rnd.nextInt(2);
            for (int i = 0; i < n; i++) c.add(impl.makeElement(i));
            Iterator it = c.iterator();
            assertTrue(it.hasNext());
            assertEquals(impl.makeElement(0), it.next());
            assertTrue(it.hasNext());
            assertEquals(impl.makeElement(1), it.next());
            it.forEachRemaining((e) -> {});
            it.remove();
            assertEquals(n - 1, c.size());
            for (int i = 0; i < n - 1; i++)
                assertTrue(c.contains(impl.makeElement(i)));
            assertFalse(c.contains(impl.makeElement(n - 1)));
        }
        if (c instanceof Deque) {
            Deque d = (Deque) impl.emptyCollection();
            int n = 3 + rnd.nextInt(2);
            for (int i = 0; i < n; i++) d.add(impl.makeElement(i));
            Iterator it = d.descendingIterator();
            assertTrue(it.hasNext());
            assertEquals(impl.makeElement(n - 1), it.next());
            assertTrue(it.hasNext());
            assertEquals(impl.makeElement(n - 2), it.next());
            it.forEachRemaining((e) -> {});
            it.remove();
            assertEquals(n - 1, d.size());
            for (int i = 1; i < n; i++)
                assertTrue(d.contains(impl.makeElement(i)));
            assertFalse(d.contains(impl.makeElement(0)));
        }
    }

    /**
     * stream().forEach returns elements in the collection
     */
    public void testStreamForEach() throws Throwable {
        final Collection c = impl.emptyCollection();
        final AtomicLong count = new AtomicLong(0L);
        final Object x = impl.makeElement(1);
        final Object y = impl.makeElement(2);
        final ArrayList found = new ArrayList();
        Consumer<Object> spy = (o) -> { found.add(o); };
        c.stream().forEach(spy);
        assertTrue(found.isEmpty());

        assertTrue(c.add(x));
        c.stream().forEach(spy);
        assertEquals(Collections.singletonList(x), found);
        found.clear();

        assertTrue(c.add(y));
        c.stream().forEach(spy);
        assertEquals(2, found.size());
        assertTrue(found.contains(x));
        assertTrue(found.contains(y));
        found.clear();

        c.clear();
        c.stream().forEach(spy);
        assertTrue(found.isEmpty());
    }

    public void testStreamForEachConcurrentStressTest() throws Throwable {
        if (!impl.isConcurrent()) return;
        final Collection c = impl.emptyCollection();
        final long testDurationMillis = timeoutMillis();
        final AtomicBoolean done = new AtomicBoolean(false);
        final Object elt = impl.makeElement(1);
        final Future<?> f1, f2;
        final ExecutorService pool = Executors.newCachedThreadPool();
        try (PoolCleaner cleaner = cleaner(pool, done)) {
            final CountDownLatch threadsStarted = new CountDownLatch(2);
            Runnable checkElt = () -> {
                threadsStarted.countDown();
                while (!done.get())
                    c.stream().forEach((x) -> { assertSame(x, elt); }); };
            Runnable addRemove = () -> {
                threadsStarted.countDown();
                while (!done.get()) {
                    assertTrue(c.add(elt));
                    assertTrue(c.remove(elt));
                }};
            f1 = pool.submit(checkElt);
            f2 = pool.submit(addRemove);
            Thread.sleep(testDurationMillis);
        }
        assertNull(f1.get(0L, MILLISECONDS));
        assertNull(f2.get(0L, MILLISECONDS));
    }

    /**
     * collection.forEach returns elements in the collection
     */
    public void testForEach() throws Throwable {
        final Collection c = impl.emptyCollection();
        final AtomicLong count = new AtomicLong(0L);
        final Object x = impl.makeElement(1);
        final Object y = impl.makeElement(2);
        final ArrayList found = new ArrayList();
        Consumer<Object> spy = (o) -> { found.add(o); };
        c.forEach(spy);
        assertTrue(found.isEmpty());

        assertTrue(c.add(x));
        c.forEach(spy);
        assertEquals(Collections.singletonList(x), found);
        found.clear();

        assertTrue(c.add(y));
        c.forEach(spy);
        assertEquals(2, found.size());
        assertTrue(found.contains(x));
        assertTrue(found.contains(y));
        found.clear();

        c.clear();
        c.forEach(spy);
        assertTrue(found.isEmpty());
    }

    public void testForEachConcurrentStressTest() throws Throwable {
        if (!impl.isConcurrent()) return;
        final Collection c = impl.emptyCollection();
        final long testDurationMillis = timeoutMillis();
        final AtomicBoolean done = new AtomicBoolean(false);
        final Object elt = impl.makeElement(1);
        final Future<?> f1, f2;
        final ExecutorService pool = Executors.newCachedThreadPool();
        try (PoolCleaner cleaner = cleaner(pool, done)) {
            final CountDownLatch threadsStarted = new CountDownLatch(2);
            Runnable checkElt = () -> {
                threadsStarted.countDown();
                while (!done.get())
                    c.forEach((x) -> { assertSame(x, elt); }); };
            Runnable addRemove = () -> {
                threadsStarted.countDown();
                while (!done.get()) {
                    assertTrue(c.add(elt));
                    assertTrue(c.remove(elt));
                }};
            f1 = pool.submit(checkElt);
            f2 = pool.submit(addRemove);
            Thread.sleep(testDurationMillis);
        }
        assertNull(f1.get(0L, MILLISECONDS));
        assertNull(f2.get(0L, MILLISECONDS));
    }

//     public void testCollection8DebugFail() {
//         fail(impl.klazz().getSimpleName());
//     }
}
Revision:	1.5
Committed:	Tue Oct 25 01:32:55 2016 UTC (7 years, 6 months ago) by jsr166
Branch:	MAIN
Changes since 1.4:	+248 -0 lines
Log Message:	fix 4jdk7-test ant target
#	User	Rev	Content
1	jsr166	1.1	/*
2			* Written by Doug Lea and Martin Buchholz with assistance from
3			* members of JCP JSR-166 Expert Group and released to the public
4			* domain, as explained at
5			* http://creativecommons.org/publicdomain/zero/1.0/
6			*/
7
8			import static java.util.concurrent.TimeUnit.MILLISECONDS;
9
10			import java.util.ArrayList;
11			import java.util.Collection;
12			import java.util.Collections;
13	jsr166	1.5	import java.util.Deque;
14			import java.util.HashSet;
15			import java.util.Iterator;
16			import java.util.List;
17			import java.util.NoSuchElementException;
18			import java.util.Queue;
19			import java.util.Spliterator;
20	jsr166	1.2	import java.util.concurrent.CountDownLatch;
21	jsr166	1.1	import java.util.concurrent.Executors;
22			import java.util.concurrent.ExecutorService;
23			import java.util.concurrent.Future;
24	jsr166	1.5	import java.util.concurrent.ThreadLocalRandom;
25	jsr166	1.1	import java.util.concurrent.atomic.AtomicBoolean;
26			import java.util.concurrent.atomic.AtomicLong;
27	jsr166	1.5	import java.util.concurrent.atomic.AtomicReference;
28	jsr166	1.1	import java.util.function.Consumer;
29	jsr166	1.5	import java.util.function.Predicate;
30	jsr166	1.1
31			import junit.framework.Test;
32
33			/**
34			* Contains tests applicable to all jdk8+ Collection implementations.
35			* An extension of CollectionTest.
36			*/
37			public class Collection8Test extends JSR166TestCase {
38			final CollectionImplementation impl;
39
40			/** Tests are parameterized by a Collection implementation. */
41			Collection8Test(CollectionImplementation impl, String methodName) {
42			super(methodName);
43			this.impl = impl;
44			}
45
46			public static Test testSuite(CollectionImplementation impl) {
47			return parameterizedTestSuite(Collection8Test.class,
48			CollectionImplementation.class,
49			impl);
50			}
51
52	jsr166	1.5	/** Checks properties of empty collections. */
53			public void testEmptyMeansEmpty() {
54			Collection c = impl.emptyCollection();
55			assertTrue(c.isEmpty());
56			assertEquals(0, c.size());
57			assertEquals("[]", c.toString());
58			{
59			Object[] a = c.toArray();
60			assertEquals(0, a.length);
61			assertSame(Object[].class, a.getClass());
62			}
63			{
64			Object[] a = new Object[0];
65			assertSame(a, c.toArray(a));
66			}
67			{
68			Integer[] a = new Integer[0];
69			assertSame(a, c.toArray(a));
70			}
71			{
72			Integer[] a = { 1, 2, 3};
73			assertSame(a, c.toArray(a));
74			assertNull(a[0]);
75			assertSame(2, a[1]);
76			assertSame(3, a[2]);
77			}
78			assertIteratorExhausted(c.iterator());
79			Consumer alwaysThrows = (e) -> { throw new AssertionError(); };
80			c.forEach(alwaysThrows);
81			c.iterator().forEachRemaining(alwaysThrows);
82			c.spliterator().forEachRemaining(alwaysThrows);
83			assertFalse(c.spliterator().tryAdvance(alwaysThrows));
84			if (Queue.class.isAssignableFrom(impl.klazz())) {
85			Queue q = (Queue) c;
86			assertNull(q.peek());
87			assertNull(q.poll());
88			}
89			if (Deque.class.isAssignableFrom(impl.klazz())) {
90			Deque d = (Deque) c;
91			assertNull(d.peekFirst());
92			assertNull(d.peekLast());
93			assertNull(d.pollFirst());
94			assertNull(d.pollLast());
95			assertIteratorExhausted(d.descendingIterator());
96			}
97			}
98
99			public void testNullPointerExceptions() {
100			Collection c = impl.emptyCollection();
101			assertThrows(
102			NullPointerException.class,
103			() -> c.addAll(null),
104			() -> c.containsAll(null),
105			() -> c.retainAll(null),
106			() -> c.removeAll(null),
107			() -> c.removeIf(null),
108			() -> c.toArray(null));
109
110			if (!impl.permitsNulls()) {
111			assertThrows(
112			NullPointerException.class,
113			() -> c.add(null));
114			}
115			if (!impl.permitsNulls()
116			&& Queue.class.isAssignableFrom(impl.klazz())) {
117			Queue q = (Queue) c;
118			assertThrows(
119			NullPointerException.class,
120			() -> q.offer(null));
121			}
122			if (!impl.permitsNulls()
123			&& Deque.class.isAssignableFrom(impl.klazz())) {
124			Deque d = (Deque) c;
125			assertThrows(
126			NullPointerException.class,
127			() -> d.addFirst(null),
128			() -> d.addLast(null),
129			() -> d.offerFirst(null),
130			() -> d.offerLast(null),
131			() -> d.push(null));
132			}
133			}
134
135			public void testNoSuchElementExceptions() {
136			Collection c = impl.emptyCollection();
137			assertThrows(
138			NoSuchElementException.class,
139			() -> c.iterator().next());
140
141			if (Queue.class.isAssignableFrom(impl.klazz())) {
142			Queue q = (Queue) c;
143			assertThrows(
144			NoSuchElementException.class,
145			() -> q.element(),
146			() -> q.remove());
147			}
148			if (Deque.class.isAssignableFrom(impl.klazz())) {
149			Deque d = (Deque) c;
150			assertThrows(
151			NoSuchElementException.class,
152			() -> d.getFirst(),
153			() -> d.getLast(),
154			() -> d.removeFirst(),
155			() -> d.removeLast(),
156			() -> d.pop(),
157			() -> d.descendingIterator().next());
158			}
159			}
160
161			public void testRemoveIf() {
162			Collection c = impl.emptyCollection();
163			ThreadLocalRandom rnd = ThreadLocalRandom.current();
164			int n = rnd.nextInt(6);
165			for (int i = 0; i < n; i++) c.add(impl.makeElement(i));
166			AtomicReference threwAt = new AtomicReference(null);
167			ArrayList survivors = new ArrayList(c);
168			ArrayList accepts = new ArrayList();
169			ArrayList rejects = new ArrayList();
170			Predicate randomPredicate = (e) -> {
171			assertNull(threwAt.get());
172			switch (rnd.nextInt(3)) {
173			case 0: accepts.add(e); return true;
174			case 1: rejects.add(e); return false;
175			case 2: threwAt.set(e); throw new ArithmeticException();
176			default: throw new AssertionError();
177			}
178			};
179			try {
180			boolean modified = c.removeIf(randomPredicate);
181			if (!modified) {
182			assertNull(threwAt.get());
183			assertEquals(n, rejects.size());
184			assertEquals(0, accepts.size());
185			}
186			} catch (ArithmeticException ok) {}
187			survivors.removeAll(accepts);
188			if (n - accepts.size() != c.size()) {
189			System.err.println(impl.klazz());
190			System.err.println(c);
191			System.err.println(accepts);
192			System.err.println(rejects);
193			System.err.println(survivors);
194			System.err.println(threwAt.get());
195			}
196			assertEquals(n - accepts.size(), c.size());
197			assertTrue(c.containsAll(survivors));
198			assertTrue(survivors.containsAll(rejects));
199			for (Object x : accepts) assertFalse(c.contains(x));
200			if (threwAt.get() == null)
201			assertEquals(accepts.size() + rejects.size(), n);
202			}
203
204			/**
205			* Various ways of traversing a collection yield same elements
206			*/
207			public void testIteratorEquivalence() {
208			Collection c = impl.emptyCollection();
209			ThreadLocalRandom rnd = ThreadLocalRandom.current();
210			int n = rnd.nextInt(6);
211			for (int i = 0; i < n; i++) c.add(impl.makeElement(i));
212			ArrayList iterated = new ArrayList();
213			ArrayList iteratedForEachRemaining = new ArrayList();
214			ArrayList spliterated = new ArrayList();
215			ArrayList foreached = new ArrayList();
216			for (Object x : c) iterated.add(x);
217			c.iterator().forEachRemaining(e -> iteratedForEachRemaining.add(e));
218			c.spliterator().forEachRemaining(e -> spliterated.add(e));
219			c.forEach(e -> foreached.add(e));
220			boolean ordered =
221			c.spliterator().hasCharacteristics(Spliterator.ORDERED);
222			if (c instanceof List \|\| c instanceof Deque)
223			assertTrue(ordered);
224			if (ordered) {
225			assertEquals(iterated, iteratedForEachRemaining);
226			assertEquals(iterated, spliterated);
227			assertEquals(iterated, foreached);
228			} else {
229			HashSet cset = new HashSet(c);
230			assertEquals(cset, new HashSet(iterated));
231			assertEquals(cset, new HashSet(iteratedForEachRemaining));
232			assertEquals(cset, new HashSet(spliterated));
233			assertEquals(cset, new HashSet(foreached));
234			}
235			if (c instanceof Deque) {
236			Deque d = (Deque) c;
237			ArrayList descending = new ArrayList();
238			ArrayList descendingForEachRemaining = new ArrayList();
239			for (Iterator it = d.descendingIterator(); it.hasNext(); )
240			descending.add(it.next());
241			d.descendingIterator().forEachRemaining(
242			e -> descendingForEachRemaining.add(e));
243			Collections.reverse(descending);
244			Collections.reverse(descendingForEachRemaining);
245			assertEquals(iterated, descending);
246			assertEquals(iterated, descendingForEachRemaining);
247			}
248			}
249
250			/**
251			* Calling Iterator#remove() after Iterator#forEachRemaining
252			* should remove last element
253			*/
254			public void testRemoveAfterForEachRemaining() {
255			Collection c = impl.emptyCollection();
256			ThreadLocalRandom rnd = ThreadLocalRandom.current();
257			{
258			int n = 3 + rnd.nextInt(2);
259			for (int i = 0; i < n; i++) c.add(impl.makeElement(i));
260			Iterator it = c.iterator();
261			assertTrue(it.hasNext());
262			assertEquals(impl.makeElement(0), it.next());
263			assertTrue(it.hasNext());
264			assertEquals(impl.makeElement(1), it.next());
265			it.forEachRemaining((e) -> {});
266			it.remove();
267			assertEquals(n - 1, c.size());
268			for (int i = 0; i < n - 1; i++)
269			assertTrue(c.contains(impl.makeElement(i)));
270			assertFalse(c.contains(impl.makeElement(n - 1)));
271			}
272			if (c instanceof Deque) {
273			Deque d = (Deque) impl.emptyCollection();
274			int n = 3 + rnd.nextInt(2);
275			for (int i = 0; i < n; i++) d.add(impl.makeElement(i));
276			Iterator it = d.descendingIterator();
277			assertTrue(it.hasNext());
278			assertEquals(impl.makeElement(n - 1), it.next());
279			assertTrue(it.hasNext());
280			assertEquals(impl.makeElement(n - 2), it.next());
281			it.forEachRemaining((e) -> {});
282			it.remove();
283			assertEquals(n - 1, d.size());
284			for (int i = 1; i < n; i++)
285			assertTrue(d.contains(impl.makeElement(i)));
286			assertFalse(d.contains(impl.makeElement(0)));
287			}
288			}
289
290	jsr166	1.1	/**
291			* stream().forEach returns elements in the collection
292			*/
293	jsr166	1.3	public void testStreamForEach() throws Throwable {
294	jsr166	1.1	final Collection c = impl.emptyCollection();
295			final AtomicLong count = new AtomicLong(0L);
296			final Object x = impl.makeElement(1);
297			final Object y = impl.makeElement(2);
298			final ArrayList found = new ArrayList();
299			Consumer<Object> spy = (o) -> { found.add(o); };
300			c.stream().forEach(spy);
301			assertTrue(found.isEmpty());
302
303			assertTrue(c.add(x));
304			c.stream().forEach(spy);
305			assertEquals(Collections.singletonList(x), found);
306			found.clear();
307
308			assertTrue(c.add(y));
309			c.stream().forEach(spy);
310			assertEquals(2, found.size());
311			assertTrue(found.contains(x));
312			assertTrue(found.contains(y));
313			found.clear();
314
315			c.clear();
316			c.stream().forEach(spy);
317			assertTrue(found.isEmpty());
318			}
319
320	jsr166	1.3	public void testStreamForEachConcurrentStressTest() throws Throwable {
321			if (!impl.isConcurrent()) return;
322			final Collection c = impl.emptyCollection();
323			final long testDurationMillis = timeoutMillis();
324			final AtomicBoolean done = new AtomicBoolean(false);
325			final Object elt = impl.makeElement(1);
326			final Future<?> f1, f2;
327			final ExecutorService pool = Executors.newCachedThreadPool();
328			try (PoolCleaner cleaner = cleaner(pool, done)) {
329			final CountDownLatch threadsStarted = new CountDownLatch(2);
330			Runnable checkElt = () -> {
331			threadsStarted.countDown();
332			while (!done.get())
333			c.stream().forEach((x) -> { assertSame(x, elt); }); };
334			Runnable addRemove = () -> {
335			threadsStarted.countDown();
336			while (!done.get()) {
337			assertTrue(c.add(elt));
338			assertTrue(c.remove(elt));
339			}};
340			f1 = pool.submit(checkElt);
341			f2 = pool.submit(addRemove);
342			Thread.sleep(testDurationMillis);
343			}
344			assertNull(f1.get(0L, MILLISECONDS));
345			assertNull(f2.get(0L, MILLISECONDS));
346			}
347
348			/**
349			* collection.forEach returns elements in the collection
350			*/
351			public void testForEach() throws Throwable {
352			final Collection c = impl.emptyCollection();
353			final AtomicLong count = new AtomicLong(0L);
354			final Object x = impl.makeElement(1);
355			final Object y = impl.makeElement(2);
356			final ArrayList found = new ArrayList();
357			Consumer<Object> spy = (o) -> { found.add(o); };
358			c.forEach(spy);
359			assertTrue(found.isEmpty());
360
361			assertTrue(c.add(x));
362			c.forEach(spy);
363			assertEquals(Collections.singletonList(x), found);
364			found.clear();
365
366			assertTrue(c.add(y));
367			c.forEach(spy);
368			assertEquals(2, found.size());
369			assertTrue(found.contains(x));
370			assertTrue(found.contains(y));
371			found.clear();
372
373			c.clear();
374			c.forEach(spy);
375			assertTrue(found.isEmpty());
376			}
377
378	jsr166	1.1	public void testForEachConcurrentStressTest() throws Throwable {
379			if (!impl.isConcurrent()) return;
380			final Collection c = impl.emptyCollection();
381	jsr166	1.2	final long testDurationMillis = timeoutMillis();
382	jsr166	1.1	final AtomicBoolean done = new AtomicBoolean(false);
383			final Object elt = impl.makeElement(1);
384	jsr166	1.2	final Future<?> f1, f2;
385			final ExecutorService pool = Executors.newCachedThreadPool();
386			try (PoolCleaner cleaner = cleaner(pool, done)) {
387			final CountDownLatch threadsStarted = new CountDownLatch(2);
388			Runnable checkElt = () -> {
389			threadsStarted.countDown();
390			while (!done.get())
391	jsr166	1.3	c.forEach((x) -> { assertSame(x, elt); }); };
392	jsr166	1.2	Runnable addRemove = () -> {
393			threadsStarted.countDown();
394			while (!done.get()) {
395			assertTrue(c.add(elt));
396			assertTrue(c.remove(elt));
397			}};
398			f1 = pool.submit(checkElt);
399			f2 = pool.submit(addRemove);
400			Thread.sleep(testDurationMillis);
401			}
402			assertNull(f1.get(0L, MILLISECONDS));
403			assertNull(f2.get(0L, MILLISECONDS));
404	jsr166	1.1	}
405
406	jsr166	1.4	// public void testCollection8DebugFail() {
407			// fail(impl.klazz().getSimpleName());
408			// }
409	jsr166	1.1	}