run pytest.main() against already-imported modules

pytest_runner.py

import pytest
from rgw_multi import tests

def run_tests(realm, user):
    tests.init_multi(realm, user) # inject dependencies

    test_modules = [tests] # more in future

    args = ['-s', '-v', '--pyargs']
    for mod in test_modules:
        args += [mod.__name__]

    plugin = loaded_module_plugin(test_modules)
    pytest.main(args, [plugin])

def loaded_module_plugin(modules):
    """ return a list of plugins for pytest.main() """

    class LoadedModule(pytest.Module):
        """ Collector for a module that has already been imported """
        def __init__(self, mod, path, parent):
            super(LoadedModule, self).__init__(path, parent)
            self.mod = mod

        def _importtestmodule(self):
            self.config.pluginmanager.consider_module(self.mod)
            return self.mod

    class LoadedModulePlugin:
        """ plugin that returns LoadedModule collectors for matching modules """
        def __init__(self, modules):
            self.modules = modules

        def pytest_pycollect_makemodule(self, path, parent):
            for mod in self.modules:
                # path is given as /path/to/foo.py, __file__ may end in .pyc
                if mod.__file__ in path.strpath:
                    return LoadedModule(mod, path, parent)
            return pytest.Module(path, parent)

    return LoadedModulePlugin(modules)