til/python/test-a-function-with-pytest.md

Test A Function With Pytest

The pytest framework is a solid choice for unit testing your python project.

Any file whose name is preceeded with test_ that contains functions whose names are preceeded with test_ will be processed and executed by the pytest test runner.

# test_taco.py

def taco(day):
  return "Taco " + day

def test_taco_tuesday():
  assert taco("Tuesday") == "Taco Tuesday" # passes

def test_taco_blank():
  assert taco("") == "Taco" # fails, missing trailing space

Use assert statements to check that a comparison is true. If it isn't the assert statement will result in a test failure with some output about what went wrong.

Ensure you have pytest installed and then run the following from your project directory:

$ pytest
#=> ... you'll see the test output below