Remove fixtures in favor of defining modules in the test cases about ex_doc

[jwarwick]

I've started to think about how to remove the test fixtures from ex_doc. I could use some guidance on the best way to proceed. It's easy enough to put all the test fixtures into test_helper.exs, though I'm not sure that's much of a win in terms of understandability. I could move individual modules into the specific test files (or even into the test functions in some cases), though I think there would be a fair amount of repeated code in those cases.

Any high-level guidance on which of these approaches makes more sense?

We will still need a small number of test fixtures to test the file and directory reading code (unless there is some advantage to auto-generating those as well).

[josevalim]

@jwarwick I think we should have a mixture of both approaches. Some fixtures could be used throughout the whole codebase and therefore should be defined in test_helper.exs but some other fixtures could be define in modules or, as you said, even in particular tests since one of the goals is to decouple the tests.

This is actually the general approach for using fixtures: a minimum global set of fixtures with variations being defined specifically for each test. :)