Throw exception when Thread.sleep() is called JUnit5

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How to mock and throw an InterruptedException when Thread.sleep() is called.

@Component
public class SomeClass
    public String myMethod() {
      // do Something
      try {
         Thread.sleep(3000);
      } catch (final InterruptedException ignored) {
         log.warn("Interrupted!", ignored);
      }
      return "Hello";
    }
}

I would want to throw an InterruptedException when Thread.sleep() is called. How can I do that with JUnit5 and Mockito

junit5 spring-boot mockito java
2 Answers

Don't attempt to use mockStatic in this case.(I failed)

For testability, you should extract a sleep method in this case(maybe even a class for sleep), it is quite similar to mocking system time with Clock.

@Component
public class SomeClass {

    public String myMethod() {
        // do Something
        try {
            sleep();
        } catch (final InterruptedException ignored) {
            log.warn("Interrupted!", ignored);
        }
        return "Hello";
    }

    void sleep() throws InterruptedException {
        Thread.sleep(3000);
    }

}

Then you can simply test it like

class SomeClassTest {
    @Test
    public void Should_logWarning_When_sleepInterrupted() throws InterruptedException {
        SomeClass someClass = spy(new SomeClass());
        doThrow(InterruptedException.class).when(someClass).sleep();
        // Do assertion...
    }
}
user_79287210

If you would like to get an InterruptedException in your code you have to simply interrupt the thread, there's no need to mock anything. An example of a simple call with interruption would be:

@Test
void interrupt() {
    var object = new SomeClass();
    // runnable passed to the thread contructor
    var thread = new Thread(object::myMethod);
    thread.start();

    thread.interrupt();
}

This results in execution of the catch body (printing the "Interrupted!" message).

user_33057370
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