Force JUnit to run one test case at a time

Question

I have a problematic situation with some quite advanced unit tests (using PowerMock for mocking and JUnit 4.5). Without going into too much detail, the first test case of a test class will always succeed, but any following test cases in the same test class fails. However, if I select to only run test case 5 out of 10, for example, it will pass. So all tests pass when being run individually. Is there any way to force JUnit to run one test case at a time? I call JUnit from an ant-script.

I am aware of the problem of dependant test cases, but I can't pinpoint why this is. There are no saved variables across the test cases, so nothing to do at @Before annotation. That's why I'm looking for an emergency solution like forcing JUnit to run tests individually.

Answer 1

I am aware of all the recommendations, but to finally answer your question here is a simple way to achieve what you want. Just put this code inside your test case:

Lock sequential = new ReentrantLock();

@Override
protected void setUp() throws Exception {
    super.setUp();
    sequential.lock();
}

@Override
protected void tearDown() throws Exception {
    sequential.unlock();
    super.tearDown();
}

With this, no test can start until the lock is acquired, and only one lock can be acquired at a time.

Answer 2

It seems that your test cases are dependent, that is: the execution of case-X affects the execution of case-Y. Such a testing system should be avoided (for instance: there's no guarantee on the order at which JUnit will run your cases).

You should refactor your cases to make them independent of each other. Many times the use of @Before and @After methods can help you untangle such dependencies.