I was mainly asking what is the best default value. I see two scenarios:

* Developers want to use the same set of fixtures for all types of tests
    - Pros: less coding effort
    - Cons: different test types may require different fixtures
    - Summary: probably good for small to medium sized projects
* Developers use different sets of fixtures for different test types:
    - Pros: more flexible and isolated.
    - Cons: greater coding effort
    - Summary: good for big projects.