jUnit creates new instance of test class for each test method

This seems to be a bit counter-intuitive. You can use setUp() and tearDown() methods to setup the test environment. On the other hand - the code can be a bit shorter and more concise. Consider those two fragments:

class SomeClassTest {

    private int veryImportantField;
    private long anotherVeryImportantField;
    
    @Before
    public void setUp() {
        veryImportantField = 10;
        anotherVeryImportantFieldi = 100L; 
    }

}

and

class SimplifiedTest {
    private int veryImportantField = 10;
    private long anotherVeryImportantField = 100L;
}

The latter is definitely cleaner and simpler to understand.

I have been using that trick for a while - but I’ve never found any actual evidence whether this is/isn’t a bug. It seemed that this behavior (even if introduced by accident) just sticked with jUnit and is not likely going to change. This is what I thought until today! While reading Martin Fowler’s blog I found this particular post. This was actually a design decision to make it this way. Long live short tests! :)