Smartmarkey Smartmarkey - 7 months ago 465
Java Question

How to mock a void static method to throw exception with Powermock?

I am trying to use Powermock and Mockito to mock a void static method to throw exception as below. But I met a problem. Unless I make the two invocations of Adder.add() with the same argument, the mocked IOException won't be thrown.

BTW, I've added @RunWith(PowerMockRunner.class) and @PrepareForTest(Adder.class) to the unit test class.

class Adder{
public static void add(int i) throws IOException{
return;
}
}

@Test
public void testAdder() throws IOException{
PowerMockito.mockStatic(Adder.class);
PowerMockito.doThrow(new IOException()).when(Adder.class);
Adder.add(12);
try {
Adder.add(11);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// assert things
}


Thanks in advance. :)

Answer is as below.

After consulting here http://code.google.com/p/powermock/issues/detail?id=278 , in fact Adder.add(12) above is part of setting up mock static method. It means when invoking Adder.add() with argument 12, IOException will be thrown. It is hard to understand, right? :) So it should be written as below.

PowerMockito.mockStatic(Adder.class);
PowerMockito.doThrow(new IOException()).when(Adder.class);
Adder.add(anyInt());

Answer

Answer is as below.

After consulting here http://code.google.com/p/powermock/issues/detail?id=278 , in fact Adder.add(12) above is part of setting up mock static method. It means when invoking Adder.add() with argument 12, IOException will be thrown. It is hard to understand, right? :) So it should be written as below.

PowerMockito.mockStatic(Adder.class);
PowerMockito.doThrow(new IOException()).when(Adder.class);
Adder.add(anyInt());

EDIT:
Link is dead, try Internet Archive one instead.