Running generated nose tests

Question

Suppose I define a testFile.py python module with as follows.

def test_evens():
    for i in range(0, 5):
        yield check_even, i, i*3

def check_even(n, nn):
    assert n % 2 == 0 or nn % 2 == 0

When I let the nose identify the tests in collect-only mode I get

testFile.test_evens(0, 0) ... ok
testFile.test_evens(1, 3) ... ok
testFile.test_evens(2, 6) ... ok
testFile.test_evens(3, 9) ... ok
testFile.test_evens(4, 12) ... ok

I can run all tests using

nosetests -v testFile:test_evens

However, what if I only want to run testFile.test_evens(2, 6) (i.e., not all the tests)?

Is there any way to do this from the command line?

Answer 1

Nose cannot do this by default, to my knowledge. Here are some options:

1. Fake it from the command line

Probably not what you're looking for, but I had to mention it. You could also create a wrapper script to simplify this:

python -c 'import testFile; testFile.check_even(2, 6)'

2. Create a custom nose test loader

This is a little more involved, but you can create a custom test loader which interprets the command-line arguments as specifying the generator to load, pulls out tests and arguments from the generator, and returns a suite containing the test(s) with the matching arguments.

Below is some example code which should give you enough to build on (runner.py):

import ast
import nose

class CustomLoader(nose.loader.TestLoader):

    def loadTestsFromName(self, name, module=None):
        # parse the command line arg
        parts = name.split('(', 1)
        mod_name, func_name = parts[0].split('.')
        args = ast.literal_eval('(' + parts[1])

        # resolve the module and function - you'll probably want to
        # replace this with nose's internal discovery methods.
        mod = __import__(mod_name)
        func = getattr(mod, func_name)

        # call the generator and gather all matching tests
        tests = []
        if nose.util.isgenerator(func):
            for test in func():
                _func, _args = self.parseGeneratedTest(test)
                if _args == args:
                    tests.append(nose.case.FunctionTestCase(_func, arg=_args))
        return self.suiteClass(tests)

nose.main(testLoader=CustomLoader)

Executing it:

% python runner.py 'testFile.test_evens(2, 6)' -v
testFile.check_even(2, 6) ... ok

% python runner.py 'testFile.test_evens(2, 6)' 'testFile.test_evens(4, 12)' -v
testFile.check_even(2, 6) ... ok
testFile.check_even(4, 12) ... ok

% python runner.py 'testFile.test_evens(1, 3)' -v
testFile.check_even(1, 3) ... FAIL