unit testing - Python unittest.TestCase execution order

Question

Is there a way in Python unittest to set the order in which test cases are run?

In my current TestCase class, some testcases have side effects that set conditions for the others to run properly. Now I realize the proper way to do this is to use setUp() to do all setup related things, but I would like to implement a design where each successive test builds slightly more state that the next can use. I find this much more elegant.

class MyTest(TestCase):

  def test_setup(self):
    # Do something

  def test_thing(self):
    # Do something that depends on test_setup()

Ideally, I would like the tests to be run in the order they appear in the class. It appears that they run in alphabetical order.

Answer 1

Don't make them independent tests - if you want a monolithic test, write a monolithic test.

class Monolithic(TestCase):
  def step1(self):
      ...

  def step2(self):
      ...

  def _steps(self):
    for name in dir(self): # dir() result is implicitly sorted
      if name.startswith("step"):
        yield name, getattr(self, name) 

  def test_steps(self):
    for name, step in self._steps():
      try:
        step()
      except Exception as e:
        self.fail("{} failed ({}: {})".format(step, type(e), e))

If the test later starts failing and you want information on all failing steps instead of halting the test case at the first failed step, you can use the subtests feature: https://docs.python.org/3/library/unittest.html#distinguishing-test-iterations-using-subtests

(The subtest feature is available via unittest2 for versions prior to Python 3.4: https://pypi.python.org/pypi/unittest2 )