changing order of unit tests in Python

As said above, normally tests in test cases should be tested in any (i.e. random) order.

However, if you do want to order the tests in the test case, apparently it is not trivial. Tests (method names) are retrieved from test cases using dir(MyTest), which returns a sorted list of members. You can use a clever (?) hack to order methods by their line numbers. This will work for one test case:

if __name__ == "__main__":
    loader = unittest.TestLoader()
    ln = lambda f: getattr(MyTestCase, f).im_func.func_code.co_firstlineno
    lncmp = lambda a, b: cmp(ln(a), ln(b))
    loader.sortTestMethodsUsing = lncmp
    unittest.main(testLoader=loader, verbosity=2)

There are also test runners which do that by themselves – I think py.test does it.

You can change the default sorting behavior by setting a custom comparison function. In unittest.py you can find the class variable unittest.TestLoader.sortTestMethodsUsing which is set to the builtin function cmp by default.

For example you can revert the execution order of your tests with doing this:

import unittest
unittest.TestLoader.sortTestMethodsUsing = lambda _, x, y: cmp(y, x)

Clever Naming.

class Test01_Run_Me_First( unittest.TestCase ):
    def test010_do_this( self ):
        assertTrue( True )
    def test020_do_that( self ):
        etc.

Is one way to force a specific order.