How do I run all Python unit tests in a directory?

With Python 2.7 and higher you don't have to write new code or use third-party tools to do this; recursive test execution via the command line is built-in. Put an __init__.py in your test directory and:

python -m unittest discover <test_directory>
# or
python -m unittest discover -s <directory> -p '*_test.py'

You can read more in the python 2.7 or python 3.x unittest documentation.

You could use a test runner that would do this for you. nose is very good for example. When run, it will find tests in the current tree and run them.

Updated:

Here's some code from my pre-nose days. You probably don't want the explicit list of module names, but maybe the rest will be useful to you.

testmodules = [
    'cogapp.test_makefiles',
    'cogapp.test_whiteutils',
    'cogapp.test_cogapp',
    ]

suite = unittest.TestSuite()

for t in testmodules:
    try:
        # If the module defines a suite() function, call it to get the suite.
        mod = __import__(t, globals(), locals(), ['suite'])
        suitefn = getattr(mod, 'suite')
        suite.addTest(suitefn())
    except (ImportError, AttributeError):
        # else, just load all the test cases from the module.
        suite.addTest(unittest.defaultTestLoader.loadTestsFromName(t))

unittest.TextTestRunner().run(suite)

This is now possible directly from unittest: unittest.TestLoader.discover.

import unittest
loader = unittest.TestLoader()
start_dir = 'path/to/your/test/files'
suite = loader.discover(start_dir)

runner = unittest.TextTestRunner()
runner.run(suite)

Well by studying the code above a bit (specifically using TextTestRunner and defaultTestLoader), I was able to get pretty close. Eventually I fixed my code by also just passing all test suites to a single suites constructor, rather than adding them "manually", which fixed my other problems. So here is my solution.

import glob
import unittest

test_files = glob.glob('test_*.py')
module_strings = [test_file[0:len(test_file)-3] for test_file in test_files]
suites = [unittest.defaultTestLoader.loadTestsFromName(test_file) for test_file in module_strings]
test_suite = unittest.TestSuite(suites)
test_runner = unittest.TextTestRunner().run(test_suite)

Yeah, it is probably easier to just use nose than to do this, but that is besides the point.