JUnit Best Practice: Different Fixtures for each @Test

Question

I understand that there are @Before and @BeforeClass, which are used to define fixtures for the @Test's. But what should I use if I need different fixtures for each @Test?

• Should I define the fixture in the @Test?
• Should I create a test class for each @Test?

I am asking for the best practices here, since both solutions aren't clean in my opinion. With the first solution, I would test the initialization code. And with the second solution I would break the "one test class for each class" pattern.

Answer 1

Tips:

1. Forget the one test class per class pattern, it has little merit. Switch to one test class per usage perspective. In one perspective you might have multiple cases: upper boundary, lower boundary, etc. Create different @Tests for those in the same class.
2. Remember that JUnit will create an instance of the test class for each @Test, so each test will get a distinct fixture (set up by the same @Before methods). If you need a dissimilar fixture you need a different test class, because you are in a different perspective (see 1.)
3. There is nothing wrong with tweaking the fixture for a particular test, but you should try to keep the test clean so it tells a story. This story should be particularly clear when the test fails, hence the different, well named @Test for each case (see 1.)