Unit testing a Java constructor that exits the application

Question

Duplicate: Java: How to test methods that call System.exit()?

I am having a bit of trouble designing a unit test for a method that exits the application by calling system.exit(). Actually, this is the constructor of a class which tests some conditions and decides to exit the application. So it is this particular eventuality that I'd like to test.

Is there a particular assert that I could use, or any other suggestions?

public MyClass(arg1, arg2, arg3){
    if(argsTestingIsOK){
        continue;       
    }else{
        System.exit(0);
    }
}

score 7 · Accepted Answer · edited Dec 29 '12 at 12:06

7

Instead of exit()-ing in the constructor, throw an IllegalArgumentException instead (since that's what's really happening) and leave it to the caller to handle the exception. The application code can be written to process the exception while the JUnit test can assert that the exception occurs.

edited Dec 29 '12 at 12:06

Peter Mortensen

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answered Jul 29 '09 at 13:51

Mike Reedell

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thanks Mike, that's a great suggestion actually! Will try that now! – denchr Jul 29 '09 at 13:54

score 4 · Answer 2 · answered Jul 29 '09 at 13:51

Don't do this in a constructor. It's a bad idea, and it's misleading to anyone using your code.

The best practice is to only use something like System.exit() in a main method or in the entry point to your application - definitely not in the middle of object construction code.

Unit testing a Java constructor that exits the application

2 Answers2