19. Professional Testing

1. Pytest

Stop using print(). Use assert.

python
def test_add():
    assert add(1, 2) == 3

2. Fixtures

Setup and teardown logic (e.g., creating a DB connection).

python
@pytest.fixture
def db():
    conn = connect()
    yield conn
    conn.close()

3. Mocking

Faking external services (APIs).