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.

Update for 2021:

Lots of modern python projects use more advanced tools like pytest. For example, pull down matplotlib or scikit-learn and you will see they both use it.

It is important to know about these newer tools because when you have more than 7000 tests you need:

• more advanced ways to summarize what passes, skipped, warnings, errors
• easy ways to see how they failed
• percent complete as it is running
• total run time
• ways to generate a test report
• etc etc

In python 3, if you're using unittest.TestCase:

• You must have an empty (or otherwise) __init__.py file in your test directory (must be named test/)
• Your test files inside test/ match the pattern test_*.py. They can be inside a subdirectory under test/, and those subdirs can be named as anything.

Then, you can run all the tests with:

python -m unittest

Done! A solution less than 100 lines. Hopefully another python beginner saves time by finding this.