Testing of expected exception

[Andrey Lavrinovic]

Hi, this is my first topic, but not the last one, as I am new in Java World
I trying to test expected someException.
Could anybody explain why test fails all the time when someException is thrown within the try block (as shown below), and it passes allright if I am not using try catch.

class someClass{
  public void someMethod(int number){
    try{
      if(number != 1)
        throw new someException
    } catch(someException e){
      // do handle
    }
  }
}

// test
@Test(expected=someException.class)
public void testExpectedException{
  someClass someClass = new someClass();
  someClass.someMethod(0);
} // fialis: AssertionFailedError

Thanks.

[Campbell Ritchie]

Welcome to the Ranch

I don't know much about that sort of test, but isn't your test method supposed to find an Exception; the catch will prevent it finding that Exception.

[Mike. J. Thompson]

When you use the 'expected' parameter of the @Test annotation you are telling JUnit to expect your test method to throw the specified exception. That exception needs to make it all the way back to the TestRunner running the test.

If you use try/catch to handle the exception then that exception will not be thrown, so your test will fail.

[Olivier Sips]

Mike. J. Thompson is right, You don't need to catch the exception in the method but rather throw the exception up the call stack.
Here is an example:

class someClass{
  public void someMethod(int number) throws new someException{
      if(number != 1)
        throw new someException
  }
}
 
// test
@Test(expected=someException.class)
public void testExpectedException{
  someClass someClass = new someClass();
  someClass.someMethod(0);
}