Unit-testing single function with large number of different inputs

[Peter Otten]

Edvard Majakari wrote:

> The problem I described above shows probably one of the best reasons why
> each test method should test only one (type of) thing, but in my special
> case I don't find that appropriate due to aforementioned reasons. Any
> suggestions? I was wondering about creating test methods dynamically
> according to the files found in the test directories (which would solve
> all the problems), but I find it a tad too complex way of solving the
> problem.

I think dynamically creating test cases is the way to go. I would subclass
TestCase to test one file and then for every file put an instance of
MyTestCase into a TestSuite. For instance:

import unittest, os

# shared implementation
class Base(unittest.TestCase):
    def __init__(self, filename):
        unittest.TestCase.__init__(self)
        self.filename = filename

# some pointless tests
class Good1(Base):
    def runTest(self):
        self.assertEqual(self.filename, self.filename.lower())

class Good2(Base):
    def runTest(self):
        self.assertEqual(self.filename.endswith(".py"), True)

class Bad(Base):
    def runTest(self):
        self.assertEqual(self.filename.endswith(".pyc"), True)

# build a test suite with (all applicable test cases) 
# x (every file in a folder, optionally including subfolders)
def makeTests(classes, folder, recursive=False):
    suite = unittest.TestSuite()
    for path, folders, files in os.walk(folder):
        for fn in files:
            for cls in classes:
                suite.addTest(cls(os.path.join(path, fn)))
        if not recursive: break
    return suite

# build the main test suite with subsuites for every folder
def makeSuite():
    suite = unittest.TestSuite()
    goodfolder = "/usr/local/lib/python2.3"
    badfolder = "/usr/local/lib/python2.3"
    suite.addTest(makeTests((Good1, Good2), goodfolder))
    suite.addTest(makeTests((Bad,), badfolder))
    return suite

if __name__ == "__main__":
    unittest.main(defaultTest="makeSuite")

Peter