Mockito How to mock and assert a thrown exception?

Question

To answer your second question first. If you're using JUnit 4, you can annotate your test with

@Test(expected=MyException.class)

to assert that an exception has occured. And to "mock" an exception with mockito, use

when(myMock.doSomething()).thenThrow(new MyException());

BDD Style Solution (Updated to Java 8)

Mockito alone is not the best solution for handling exceptions, use Mockito with Catch-Exception

Mockito + Catch-Exception + AssertJ

given(otherServiceMock.bar()).willThrow(new MyException());

when(() -> myService.foo());

then(caughtException()).isInstanceOf(MyException.class);

Sample code

• Mockito + Catch-Exception + Assertj full sample

Dependencies

• eu.codearte.catch-exception:catch-exception:2.0
• org.assertj:assertj-core:3.12.2

If you want to test the exception message as well you can use JUnit's ExpectedException with Mockito:

@Rule
public ExpectedException expectedException = ExpectedException.none();

@Test
public void testExceptionMessage() throws Exception {
    expectedException.expect(AnyException.class);
    expectedException.expectMessage("The expected message");

    given(foo.bar()).willThrow(new AnyException("The expected message"));
}

Updated answer for 06/19/2015 (if you're using java 8)

Just use assertj

Using assertj-core-3.0.0 + Java 8 Lambdas

@Test
public void shouldThrowIllegalArgumentExceptionWhenPassingBadArg() {
assertThatThrownBy(() -> myService.sumTingWong("badArg"))
                                  .isInstanceOf(IllegalArgumentException.class);
}

Reference: http://blog.codeleak.pl/2015/04/junit-testing-exceptions-with-java-8.html

If you're using JUnit 4, and Mockito 1.10.x Annotate your test method with:

@Test(expected = AnyException.class)

and to throw your desired exception use:

Mockito.doThrow(new AnyException()).when(obj).callAnyMethod();