How to mock out Thread.sleep() with JMockit?

Question

I have the following code:

class Sleeper {
    public void sleep(long duration) {
        try {
            Thread.sleep(duration);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    }
}

How do I test, with JMockit, that Thread.currentThread().interrupt() is called if Thread.sleep() throws an InterruptedException?

score 3 · Accepted Answer · answered Aug 21 '11 at 20:31

Interesting question. A bit tricky to test because mocking certain methods of java.lang.Thread can interfere with the JRE or with JMockit itself, and because JMockit is (currently) unable to dynamically mock native methods such as sleep. That said, it can still be done:

public void testResetInterruptStatusWhenInterrupted() throws Exception
{
    new Expectations() {
       @Mocked({"sleep", "interrupt"}) final Thread unused = null;

       {
           Thread.sleep(anyLong); result = new InterruptedException();
           onInstance(Thread.currentThread()).interrupt();
       }
    };

    new Sleeper.sleep();
}

Small comment with an update as it now (jmockit 1.28, but probably starting some versions before) looks different (taken/inspired from/by the JREMockingTest.java sample of JMockit): `@Test public void callThreadSleepOnceSomewhere(@Mocked Thread unused) throws Exception { new Expectations() {{ Thread.sleep(anyLong); times = 1; }}; // your code calling Thread.sleep(...) once }` — AntiTiming, Oct 03 '16 at 16:58

score 1 · Answer 2 · answered Mar 08 '19 at 22:03

1

As of JMockit 1.43, this is impossible

JMockit 1.43 added this commit, which checks if you are trying to mock a thread and blacklists it. Now you will get this exception:

java.lang.IllegalArgumentException: java.lang.Thread is not mockable

answered Mar 08 '19 at 22:03

Thunderforge

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How to mock out Thread.sleep() with JMockit?

2 Answers2

As of JMockit 1.43, this is impossible