Can I nest TestCases with Nose?

Question

I've become a fan of nested test case contexts in things like RSpec and Jasmine, and I'm wondering if there are any Nose plugins that implement a test finder that allows you to nest classes as context. The resulting tests would look something like the following:

from nose.tools import *
from mysystem import system_state

class TestMySystem (TestCase):
    def setUp(self):
        system_state.initialize()

    class WhenItIsSetTo1 (TestCase):
        def setUp(self):
            system_state.set_to(1)

        def test_system_should_be_1 (self):
            assert_equal(system_state.value(), 1)

    class WhenItIsSetTo2 (TestCase):
        def setUp(self):
            system_state.set_to(2)

        def test_system_should_be_2 (self):
            assert_equal(system_state.value(), 2)

In the above hypothetical case, system_state.initialize() will be called before each test. I know there is PyVows for doing something like this, and it looks good, but I'm looking for something to plug in to my current project, which already has a number of unittest-/nose-style tests.

Answer 1

It sounds like you want some of your test to inherit setup code from other tests:

from nose.tools import *
from mysystem import system_state

class TestMySystem (TestCase):
    def setUp(self):
        system_state.initialize()

class WhenItIsSetTo1 (TestMySystem):
    def setUp(self):
        super(WhenItIsSetTo1, self).setUp()
        system_state.set_to(1)

    def test_system_should_be_1 (self):
        assert_equal(system_state.value(), 1)

class WhenItIsSetTo2 (TestMySystem):
    def setUp(self):
        super(WhenItIsSetTo2, self).setUp()
        system_state.set_to(2)

    def test_system_should_be_2 (self):
        assert_equal(system_state.value(), 2)

Be careful when you do this; if you have actual test methods in the parent class, they will also be executed when the child is run (of course). When I do this, I like to make pure parent test classes that only provide setUp, tearDown & classSetup/ classTearDown.

This should allow you an arbitrary level of nesting, though once you do that you're going to need unit tests for your unit tests...

Answer 2

Not as far as I know, but you can achieve a similar effect with setup and teardown methods at the module and package levels.

Your example would then become:

def setup():
    system_state.initialize()

def teardown():
    system_state.teardown()

class WhenItIsSetTo1 (TestCase):
    def setUp(self):
        system_state.set_to(1)

    def test_system_should_be_1 (self):
        assert_equal(system_state.value(), 1)

class WhenItIsSetTo2 (TestCase):
    def setUp(self):
        system_state.set_to(2)

    def test_system_should_be_2 (self):
        assert_equal(system_state.value(), 2)