Test discovery rules (common pattern)

Unittest can discover tests when:

• files match test*.pytest*.py
• tests are under a folder like tests/tests/
• test methods start with test_test_

Typical project layout

project/
  src/
    app.py
  tests/
    test_app.py

project/
  src/
    app.py
  tests/
    test_app.py

Running discovery

From the project root:

python -m unittest discover

python -m unittest discover

To specify a tests folder:

python -m unittest discover -s tests

python -m unittest discover -s tests

Run a specific test module

python -m unittest tests.test_app

python -m unittest tests.test_app

Tip

If discovery finds 0 tests, check:

• filenames
• class inherits from unittest.TestCaseunittest.TestCase
• methods start with test_test_

🧪 Try It Yourself

Exercise 1 – Write a unittest TestCase

Exercise 2 – assertRaises

Exercise 3 – setUp and tearDown