What s the actual use of fail in JUnit test case

Question

What s the actual use of  fail  in JUnit test case

User · Answer

I think the usual use case is to call it when no exception was thrown in a negative test.

Something like the following pseudo-code:

test_addNilThrowsNullPointerException()
{
    try {
        foo.add(NIL);                      // we expect a NullPointerException here
        fail("No NullPointerException");   // cause the test to fail if we reach this            
     } catch (NullNullPointerException e) {
        // OK got the expected exception
    }
}

User · Answer

I  for example  use fail   to indicate tests that are not yet finished  it happens   otherwise  they would show as successful   This is perhaps due to the fact that I am unaware of some sort of incomplete   functionality  which exists in NUnit

User · Answer

Let s say you are writing a test case for a negative flow where the code being tested should raise an exception  try     bizMethod badData      fail       FAIL when no exception is thrown   catch  BizException e       assert e errorCode    THE ERROR CODE U R LOOKING FOR

User · Answer

Some cases where I have found it useful    mark a test that is incomplete  so it fails and warns you until you can finish it making sure an exception is thrown     try       do stuff      fail  Exception not thrown     catch Exception e     assertTrue e hasSomeFlag          Note   Since JUnit4  there is a more elegant way to test that an exception is being thrown  Use the annotation  Test expected IndexOutOfBoundsException class   However  this won t work if you also want to inspect the exception  then you still need fail

User · Answer

This is how I use the Fail method   There are three states that your test case can end up in   Passed   The function under test executed successfully and returned data as expected  Not Passed   The function under test executed successfully but the returned data was not as expected Failed   The function did not execute successfully and this was not   intended  Unlike negative test cases that expect a exception to     occur    If you are using eclipse there three states are indicated by a Green  Blue and red marker respectively   I use the fail operation for the the third scenario   e g    public Integer add integer a  Integer b    return new Integer a intValue     b intValue       Passed Case   a   new Interger 1   b  new Integer 2  and the function returned 3 Not Passed Case  a   new Interger 1   b  new Integer 2  and the function returned soem value other than 3 Failed Case   a  null   b  null and the function throws a NullPointerException

User · Answer

The most important use case is probably exception checking   While junit4 includes the expected element for checking if an exception occurred  it seems like it isn t part of the newer junit5  Another advantage of using fail   over the expected is that you can combine it with finally allowing test-case cleanup   dao insert obj   try     dao insert obj     fail  No DuplicateKeyException thrown       catch  DuplicateKeyException e      assertEquals  Error code doesn t match   123  e getErrorCode       finally       cleanup   dao delete obj       As noted in another comment  Having a test to fail until you can finish implementing it sounds reasonable as well

User · Answer

In concurrent and or asynchronous settings  you may want to verify that certain methods  e g  delegates  event listeners  response handlers  you name it  are not called  Mocking frameworks aside  you can call fail   in those methods to fail the tests  Expired timeouts are another natural failure condition in such scenarios   For example   final CountDownLatch latch   new CountDownLatch 1    service asyncCall someParameter  new ResponseHandler lt SomeType gt           Override     public void onSuccess SomeType result            assertNotNull result              Further test assertions on the result         latch countDown                Override     public void onError Exception e            fail exception getMessage             latch countDown               if    latch await 5  TimeUnit SECONDS          fail  No response after 5s

User · Answer

I ve used it in the case where something may have gone awry in my  Before method   public Object obj    Before public void setUp            Do some set up     obj   new Object        Test public void testObjectManipulation         if obj    null            fail  obj should not be null                   Do some other valuable testing

[java] What's the actual use of 'fail' in JUnit test case?

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