python > pytest, ptw (watch mode) and setting up unit testing for python

abstract

The concern is documenting finding the unit test framework similar to jest for javascript.

1. pytest

• install

pip install -U pytest

• validate

pytest --version
pytest 6.0.1

2. pytest-watch

• install pytest-watch to enable tehe watch mode for pytest, i.e. make pytest run each time you save the file in the watched folder

pip install pytest-watch

• validate

ptw --version
pytest-watch 4.2.0

3. test1: code & test in the same file

• create a file *_test.py and write a first function & corresponding test
• run ptw to run pytest in a watch mode

def func(x):
    return x + 1

def test_answer():
    assert func(3) == 4

4. test2: import sourcefile into testfile

import addition

def test_answer1():
    input = 4                     # arrange
    result = addition.func(input) # act
    assert result == 8            # assert

debug: use vscode

• python extension needs to be activated
• run Python > configure tests to select testing framework and folder with files (no drill-down here)
• open the file (here both source and test in a single file)
• set a breakpoint and click on Debug test in the file → do not run debugger with f5 or from the sidebar

Originally published at http://pavol.kutaj.com on August 11, 2020.