Unit Testing

The TestNG Eclipse plugin has a feature that will convert your unit tests from JUnit to TestNG in a few simple clicks, and it works pretty well for the most part. However, I soon noticed that it was replacing Assert.assertX with AssertJUnit.assertX. Upon further inspection, this was because TestNG’s Assert uses different argument ordering. For example

// JUnit  
Assert.assertEquals(message, expected, actual);

// TestNG  
Assert.assertEquals(actual, expected, message);  

Each argument has moved.

Non-deterministic unit tests are like kryptonite for an automated build. They cause intermittent build failures and the development team becomes accustomed to ignoring a failing build. This is a Bad Thing.

Thread.sleep(x) in a unit test is a recipe for non-deterministic behaviour. Think about what happens when this test is run on a slow machine. How big does X need to be?

I often see this anti-pattern in multi-threaded code where the test case is waiting for some asynchronous task to complete, and the test case has to guess at how long the task will take, and then asserts on some condition that the task was supposed to change.