How to mock Thread.sleep() with PowerMock?

This took me a while to figure out, so I am answering my own question.

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)  // important
@PrepareForTest(MachineImpl.class)  // important: do not use Thread.class here
public class MachineImplTest {

    private MachineImpl classUnderTest;

    @Before
    public void beforeEachTest() {
        classUnderTest = new MachineImpl();
    }

    @Test
    public void sleep_Pass() {
        classUnderTest.sleep(0);
        classUnderTest.sleep(-100);
        classUnderTest.sleep(+100);
    }

    @Test
    public void sleep_Pass2() {
        // We do not want to mock all methods, only specific methods, such as Thread.sleep().
        // Use spy() instead of mockStatic().
        PowerMockito.spy(Thread.class);

        // These two lines are tightly bound.
        PowerMockito.doThrow(new InterruptedException()).when(Thread.class);
        Thread.sleep(Mockito.anyLong());

        classUnderTest.sleep(0);
        classUnderTest.sleep(-100);
        classUnderTest.sleep(+100);
    }
}

If you are using TestNG, try this:

import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.testng.PowerMockTestCase;

@PrepareForTest(MachineImpl.class)  // important: do not use Thread.class here
public class MachineImplTest
extends PowerMockTestCase {
    ...
}

Read more about TestNG + Mockito + PowerMock here: https://stackoverflow.com/a/35815153/257299

This was helpfull. I did end up using something slightly different. I use EasyMock instead of Mockito.

@RunWith(PowerMockRunner.class)
@PrepareForTest({ClassUnderTest.class})
public class MyTest {
    @Before
    public void setUp() {
        PowerMock.mockStatic(Thread.class, methods(Thread.class, "sleep"));
        Thread.sleep(anyLong());
        EasyMock.expectLastCall().anyTimes();
    }
}

No need to use Thread.class in @PrepareForTest.