Porting tests to Pytest

##Introduction Software testing is extremely important to the MDAnalysis project, so that users of the package can be confident in the results of their analysis. With the current test package nose, ceasing to be developed we have decided to move to using py.test.

Current state

There are a total of 4731 test cases(that nose executes). Running the testsuite, with pytest gives the following output: 1789 failed, 2630 passed, 52 skipped, 1610 pytest-warnings, 26 error

How?

Existing Plugins and how to import them

Tests passing with pytests

Tests failing currently

• Classes with __init__ methods are not collected for test cases.

Examples of failed tests

Where can we replace nose with pytest