期望Exception.class的TestNG类

Question

I have inherited some code from another team which uses

@Test (expectedExceptions = {Exception.class})

everywhere when the code might be throwing a more specific exception.

My understanding is that this is wrong because we are not expecting the right type of exception. But the current owners are saying that they have seen no issue because of this.

Is my understanding correct?

Answer 1

This is poor design, since it could be masking errors other than the one being tested for. As an example, suppose your code should throw a SecurityException on some operation but instead is throwing a NullPointerException because of a naive dereference. Your test would pass when it should fail.

You should always make your matchers as specific as possible, and in this case, that means the most specific exception class that applies.

Answer 2

Exception is Parent class of all types of exception in java, so basically your test will pass if code throws any checked or unchecked exception. But its better to write unit test that will expect a particular type of exception which your code can throw. For eg let say your have a method to validateParam

public void validateParam(String param) throws SomeCustomValidationException {
  //suppose param is null , now this code will throw NullPointerException
  if (param.length() > 2) {throw new SomeCustomValidationException();}
}

and you call it like this

public void businessLogic(String param)  {
   try {validateParam(param);}
   catch(SomeCustomValidationException e){//show error dialog to the user} 
}

So although your unit test will pass but your business logic will not work as you expected