Testing simple multithread code using EasyMock but got strange result

Question

I am testing a simple multithread code using EasyMock:

source code:

public class EasyMockTest {

    ExecutorService executorService;
    TestObject testObject;

    public EasyMockTest(ExecutorService executorService, TestObject testObject)
    {
        this.executorService = executorService;
        this.testObject = testObject;
    }
    public void test()
    {
        try
        {
            executorService.submit(() ->{
                testObject.doSomething(); 
            });
        }
        catch(RejectedExecutionException ex)
        {
        }
     }
}


public class TestObject {

    public void doSomething()
    {
    }
}

Test code with EasyMock:

public class EasyMockTest_test {

    private TestObject testObject;
    private ExecutorService executorService;
    private EasyMockTest easyMockTest;

    @Before
    public void setUp()
    {
        executorService = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(1));
        testObject = EasyMock.createMock(TestObject.class);
        easyMockTest = new EasyMockTest(executorService, testObject);
    }

    @Test
    public void test_easyMockTest()
    {
        testObject.doSomething(); 
        EasyMock.expectLastCall().andAnswer(new IAnswer<Void>(){
            @Override
            public Void answer() throws Throwable {
                Thread.sleep(100);
                return null;
            }}).times(2);

        EasyMock.replay(testObject);
        easyMockTest.test();
        easyMockTest.test();
        easyMockTest.test();

        EasyMock.verify(testObject);
    }
}

I think in this case testObject.doSomething() should only be called twice. Since thread pool has one thread and queue size is one, and I let first two thread sleep. So when I submit three task, the third one should be rejected and the first two should be called. But when I run this code there is error:

java.lang.AssertionError:
Expectation failure on verify: TestObject.doSomething(): expected: 2, actual: 1 at org.easymock.internal.MocksControl.verify(MocksControl.java:225) at org.easymock.EasyMock.verify(EasyMock.java:2007) ...

This means the method is only called once, which i can't understand.

I also tried comment Thread.sleep(100); this times actual calling times becomes 2, butI think it should be 3 since no thread is sleeping.

Then I tried move .times() position like this:

EasyMock.expectLastCall().times(2).andAnswer(new IAnswer<Void>(){
        @Override
        public Void answer() throws Throwable {
            Thread.sleep(100);
            return null;
        }});

This time error becomes:

java.lang.AssertionError: Expectation failure on verify: TestObject.doSomething(): expected: 3, actual: 2

Why result is expecting 3 when i give it 2?

Sorry I am not expert on EasyMock, really appreciate if someone can help.

Answer 1

Nothing is making sure your tasks are executed before the verify is reached. You need something to pace the execution.

This works:

@Test public void test_easyMockTest() throws InterruptedException { CountDownLatch latch = new CountDownLatch(3);

testObject.doSomething();
EasyMock.expectLastCall().andAnswer(new IAnswer<Void>(){
  @Override
  public Void answer() throws Throwable {
    latch.countDown();
    return null;
  }}).times(2);

EasyMock.replay(testObject);
easyMockTest.test();
easyMockTest.test();
easyMockTest.test();

latch.await(1, TimeUnit.SECONDS);

EasyMock.verify(testObject);

}

Here I am assuming that you really want a RejectedExecutionException to be caught and ignored.