With jUnit 4, can I parameterize @BeforeClass?

Question

I am using jUnit to manage integration tests for an application that accesses a database. Because setting up the test data is a time-consuming operation, I have been doing that in the @BeforeClass method, which is executed only once per test class (as opposed to the @Before method, which is run once per test method).

Now I want to try a few different permutations for the configuration of the data layer, running all of my tests on each different configuration. This seems like a natural use of the Parameterized test runner. Problem is, Parameterized supplies parameters to the class constructor, and the @BeforeClass method is abstract and is called before the class constructor.

A few questions,

Does Parameterized call the @BeforeClass method for each permutation of parameters, or does it only call once?

If the @BeforeClass method is called repeatedly, is there some way to access the parameter values from inside of it?

If none of these, what do people suggest as the best alternative approach to this problem?

Answer 1

I think you are going to need a custom test runner. I'm having the same issue you are having (needing to run the same tests using multiple, expensive configurations). You'd need a way to parameterize the set up, perhaps using @Parameter annotations similar to those used by the Parameterized runner but on static member fields instead of instance fields. The custom runner would have to find all static member fields with the @Parameter annotation and then run the test class (probably using the basic BlockJunit4ClassRunner) once per static @Parameter field. The @Parameter field should probably be a @ClassRule.

Andy on Software has done a good job of developing custom test runners, and he explains so pretty clearly in these blog posts here and here.

Answer 2

@BeforeClass is only called once in your example. Which makes sense given the name - before class!

If your tests require different data, there are two choices I can think of:

1. Set up that data in @Before so it is test specific
2. Group the tests that you want to run with the same data into separate test classes and use @BeforeClass for each one.