How to run initialization code before tests when using Python's unittest module as a testrunner?

Question

How can a user of a library run his own initialization code (setting debug levels of loggers for example) before running tests supplied with the library? Python's unittest module is used as a testrunner.

Answer 1

You can try using pytest to run the unittests. If that works (many unittest based test suites work), then you can create a little module, for example "mymod.py", defining a pytest configuration hook:

# content of mymod.py
def pytest_configure():
    import logging
    logging.getLogger().setLevel(logging.WARN)

If you now execute py.test like this:

$ py.test -p mymmod --pyargs mylib

Then the "mylib" package will be searched for tests and ahead of running them the logging level is modified. The "-p" option specifies a plugin to load and the "--pyargs" tells pytest to try importing the arguments first, instead of treating them as directory or file names (the default).

For more info: http://pytest.org and http://pytest.org/latest/unittest.html

HTH, holger

Answer 2

You could do the set-up work before calling unittest.main.

Or you could subclass the test suite and run a class-level setup method.

Or you could have the test setup incorporate a callback to a user-defined setup method.

Answer 3

Answer from similar question is more helpful here:

How to a run a specific code before & after each unit test in python

I used python setUpClass method https://docs.python.org/2/library/unittest.html#unittest.TestCase.setUpClass

setUpClass()
A class method called before tests in an individual class are run. setUpClass is called with the class as the only argument and must be decorated as a classmethod():

@classmethod
def setUpClass(cls):
    ...

I run my tests like this:

python -m unittest discover -v