how to troubleshoot intermittent junit test failures?

I am dealing with a case where my tests pass or fail based on the order of declaration. This of-course points to not properly isolated tests. But I am stumped about how to go about finding the issue. The thing is my junit tests derive from a class that is belongs to a testing framework built on junit and has some dependency injection container. The container gets reset for every test by the base class setup and so there are no lingering objects at least in the container since the container itself is new. So I am 开发者_开发问答leaning toward the following scenario.

1. test1 indirectly causes some classA which sets up classA.somestaticMember to xyz value. test obj does not maintain any references to classA directly- but classA is still loaded by vm with a value xyz when test1 ends.
2. test2 access classA and trips up on somestaticmember having xyz value.

The problem is a) I dont know if this is indeed the case- how do I go about finding that ? I cannot seem to find a reference to a static var in the code... b) is there a way to tell junit to dump all its loaded classes and do it afresh for every test method ?

You can declare a method with @Before, like

@Before public void init()
{
    // set up stuff
}

and JUnit will run it before each test. You can use that to set up a "fixture" (a known set of fresh objects, data, etc that your tests will work with independently of each other).

There's also an @After, that you can use to do any cleanup required after each test. You don't normally need to do this, as Java will clean up any objects you used, but it could be useful for restoring outside objects (stuff you don't create and control) to a known state.

(Note, though: if you're relying on outside objects in order to do your tests, what you have isn't a unit test anymore. You can't really say whether a failure is due to your code or the outside object, and that's one of the purposes of unit tests.)