Cannot run individual tests with nosetests

[omaciel]

Seems that you cannot run an individual ddt test via nosetests:

$ cat test_foo.py
import unittest
from ddt import ddt, data


@ddt
class FooTestCase(unittest.TestCase):

    @data(3, 4, 12, 23)
    def test_larger_than_two(self, value):
            self.assertTrue(value > 0)

$ nosetests -vv test_foo.py:FooTestCase
nose.config: INFO: Ignoring files matching ['^\\.', '^_', '^setup\\.py$']
test_larger_than_two_12 (tests.cli.test_foo.FooTestCase) ... ok
test_larger_than_two_23 (tests.cli.test_foo.FooTestCase) ... ok
test_larger_than_two_3 (tests.cli.test_foo.FooTestCase) ... ok
test_larger_than_two_4 (tests.cli.test_foo.FooTestCase) ... ok

----------------------------------------------------------------------
Ran 4 tests in 0.001s

OK

$ nosetests -vv test_foo.py:FooTestCase.test_larger_than_two
nose.config: INFO: Ignoring files matching ['^\\.', '^_', '^setup\\.py$']
Failure: ValueError (No such test FooTestCase.test_larger_than_two) ... ERROR

======================================================================
ERROR: Failure: ValueError (No such test FooTestCase.test_larger_than_two)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/nose/failure.py", line 41, in runTest
    raise self.exc_class(self.exc_val)
ValueError: No such test FooTestCase.test_larger_than_two

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (errors=1)

[txels]

DDT creates four tests out of one, as you can see in output these are named:

test_larger_than_two_12
test_larger_than_two_23
test_larger_than_two_3
test_larger_than_two_4

So test_larger_than_two is no longer an individual test (that was kind of the whole point of ddt).
From what I've gathered, there is no way to issue a nosetests command-line that would run these four tests (e.g. by matching function name with a regex).

That said, you should be able to run them individually:

nosetests -vv test_foo.py:FooTestCase.test_larger_than_two_4

But nose still fails with:

$ nosetests -v test/test_example.py:FooTestCase.test_larger_than_two_4
Failure: ValueError (no such test method in <class 'test.test_example.FooTestCase'>: test_larger_than_two) ... ERROR

======================================================================
ERROR: Failure: ValueError (no such test method in <class 'test.test_example.FooTestCase'>: test_larger_than_two)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/carles/.virtualenvs/ddt/local/lib/python2.7/site-packages/nose/loader.py", line 518, in makeTest
    return self._makeTest(obj, parent)
  File "/home/carles/.virtualenvs/ddt/local/lib/python2.7/site-packages/nose/loader.py", line 572, in _makeTest
    return parent(obj.__name__)
  File "/usr/lib/python2.7/unittest/case.py", line 191, in __init__
    (self.__class__, methodName))
ValueError: no such test method in <class 'test.test_example.FooTestCase'>: test_larger_than_two

----------------------------------------------------------------------
Ran 1 test in 0.000s

FAILED (errors=1)

So it may be something related with how nose loads/runs the tests when running an individual method. I'll try to debug and see if something can be done within ddt.

[omaciel]

Thank you @txels for the explanation (totally makes sense to me). Since I usually generate random data for my tests, it would be impossible to know ahead of time what the test name would be. I really appreciate anything you can do to help :)

[txels]

I've been able to fix this. Turns out there was a mismatch between the new function as attribute in the test class and the function name of said function. Released as 0.7.1

Now I can do:

$ nosetests -s -v test/test_example.py:FooTestCase.test_larger_than_two_3
test_larger_than_two_3 (test.test_example.FooTestCase) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

Or even:

$ nosetests -s -v 'test/test_example.py:FooTestCase.test_tuples_extracted_into_arguments_(3, 2)'
test_tuples_extracted_into_arguments_(3, 2) (test.test_example.FooTestCase) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.000s

But unfortunately nosetests doesn't allow me to select all functions matching a name... (something like FooTestCase.test_larger_than_two*). Will have to submit a patch to nose for that ;)

[omaciel]

Though this won't help me with my scenario (where @DaTa uses random values every time), I'm glad you fixed the other use case :) Cheers!