Can we verify, no excpetion occured in a method from unit testing

Question

ATest.java - Can we verify, when no exception occurred in a testdisplay2() method like we use expected when some exception occurred in testdisplay1()

class A{
  public void display(){
    ...
    ...
    ...
    if(a){
     throw new AIsTrueException("a true");
    }

    if(b){
     throw new BIsTrueException("b true");
    }

  }
}

class BTest{
...
@InjectMock
A subject;
...
@Test(expected=AIsTrueException.class)
public void testdisplay1(){
    subject.display(true,false);
}

@Test
public void testdisplay2(){
    subject.display(false,false);
    // Here how can I verify that no exception has occured in display(),
    // (When exception occured we use expected = ...)
    // Do we have similar when no exception occured
} 
...
...
}

If an exception ocurred that shouldn't have happened, the test will fail in itself — Jaims, May 03 '17 at 10:23
you could change the return type of the display method to an int or something which will only be returned if no exception was thrown and check if the retuned value exists — XtremeBaumer, May 03 '17 at 10:23
You may rename your test method to convey the expected behavior, e.g.: `displayDoesNotThrowExceptionWhenBothParametersAreFalse()` — Timothy Truckle, May 03 '17 at 10:25
@XtremeBaumer Yes if I change the return type then I can use assert the return value. But here the return type is void that I can not change. Is there anyway, I can test that the particular exception does not occurred. — Jayanand Raghuwanshi, May 03 '17 at 11:02
you can try `expected!=AIsTrueException.class||BIsTrueException.class` never tried it myself. might work — XtremeBaumer, May 03 '17 at 11:04

score 1 · Answer 1 · answered May 03 '17 at 10:23

1

What you have is correct. Try changing display() to always throw an AIsTrueException and you will see that testdisplay2() gives an error.

answered May 03 '17 at 10:23

Chrs

862
6
10

score 1 · Answer 2 · edited May 23 '17 at 12:26

1

The expected behaviour is that no exception will be thrown. If any is thrown the test will fail unless there is an expected parameter in the annotation like the one you have in the testdisplay1 test.

Also, this is a nice read: How to test that no exception is thrown?

edited May 23 '17 at 12:26

Community

1
1

answered May 03 '17 at 10:23

Marc

356
1
8

Yes if any exception is thrown... we use expected. But here I want to verify that no exception is thrown from the method. – Jayanand Raghuwanshi May 03 '17 at 11:04
well, if there is any exception being thrown the test will fail. So, if the test succeeds it means that NO exception was thrown. – Marc May 03 '17 at 11:10
Yes you are correct. But can't we have any way to verify that using some code. – Jayanand Raghuwanshi May 03 '17 at 11:19
Anyways thank you.. I will go with that, If tests succeeds... no exception is thrown.. – Jayanand Raghuwanshi May 03 '17 at 11:20

Can we verify, no excpetion occured in a method from unit testing

2 Answers2