Python: nosetests on project containing baseclasses

I have a package I've created which contains a base class, from which future projects will inherit. I'm trying to automate testing, and have turned to nosetests.

I am a novice to Python, so apologies if my issue lies is something trivial/rudimentary.

This project leverages the popular Python Finite State Machine package transitions, from which my base class inherits State (as seen in my states.py).

Upon running $nosetests from within base_tester/, I receive 3 repeated errors (only 1 pasted for brevity):

E.EE.
======================================================================
ERROR: Failure: TypeError (__init__() missing 1 required positional argument: 'name')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/user/.pyenv/versions/3.7.1/lib/python3.7/site-packages/nose/failure.py", line 39, in runTest
    raise self.exc_val.with_traceback(self.tb)
  File "/home/user/.pyenv/versions/3.7.1/lib/python3.7/site-packages/nose/loader.py", line 523, in makeTest
    return self._makeTest(obj, parent)
  File "/home/user/.pyenv/versions/3.7.1/lib/python3.7/site-packages/nose/loader.py", line 582, in _makeTest
    return MethodTestCase(obj)
  File "/home/user/.pyenv/versions/3.7.1/lib/python3.7/site-packages/nose/case.py", line 346, in __init__
    self.inst = self.cls()
  File "/home/user/repos/openrov/production/testers/base_tester/base_tester/states.py", line 6, in __init__
    super().__init__(*args, **kwargs)
TypeError: __init__() missing 1 required positional argument: 'name'

However, when I create a small test project, and implement an inheriting class, it works as intended. I'm left to believe there's something wrong with what I'm doing in test.py, but cannot figure out what.

Thank you!

Project structure:

base_tester/
├── base_tester/
│   ├── __init__.py
│   └── states.py
├── setup.py
└── test/
    ├── __init__.py
    └── test.py

states.py:

from transitions import State

# Parent class
class TestParent(State):    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    # To be implemented by inheriting classes
    def run_test(self):
        raise NotImplementedError()

base_tester/init.py:

from base_tester.states import *

test/test.py:

import unittest
from base_tester import TestParent

class Test1(TestParent):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def run_test(self):
        pass

class Tester(unittest.TestCase):
    test1 = Test1(name='test1')

    def test_1(self):
        self.assertTrue(True)

    def main(self):
        pass

if __name__ == '__main__':
    unittest.main()

Solution

The problem lies within the naming of methods in TestParent and Test1. More specifically, it is Test1/TestParent.run_test that causes trouble. I assume that nose considers these methods to be isolated tests. As a result it tries to create an instance of the class in question and fails since TestParent,Test1 and State have no default name.

See the docs about finding tests. It mentions:

If it looks like a test, it’s a test. Names of directories, modules, classes and functions are compared against the testMatch regular expression, and those that match are considered tests. Any class that is a unittest.TestCase subclass is also collected, so long as it is inside of a module that looks like a test.

That's also the reason why you get the error message multiple times. Your output suggests that you (attempt to) run five tests from which three fail. I only got 4 but also three failing tests. To illustrate the discovery a bit better I added a default name to TestParent and let TestParent.run_test pass. If I execute nosetests -v now I get the following output:

base_tester.TestParent.run_test ... ok
test.test.Test1.run_test ... ok
test.test.TestParent.run_test ... ok
test_1 (test.test.Tester) ... ok

TestParent.run_test is executed twice due to the import. A simple solution would be to avoid method names that match the test pattern regular expression (mentioned in the docs) which by default is (?:\b|_)[Tt]est. Sometimes however having test in method names cant be avoided for semantical reasons.

The test discovery mentions the following:

If an object defines a __test__ attribute that does not evaluate to True, that object will not be collected, nor will any objects it contains.

In your case adding __test__ = False to TestParent should solve the issue as well:

# Parent class
class TestParent(State):
    __test__ = False  # avoid nosetests test discover

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    # To be implemented by inheriting classes
    def run_test(self):
        raise NotImplementedError()