Testing and pytest

Testing

For most projects you should write automated tests. You should if you value your time anyway.

Testing

Much better to catch a bug locally from the tests than getting a call at 2:00 in the morning and fix it then.

Testing

Often I find myself saving time when I put time in to write tests. It may or may not take longer to implement what I'm building, but I (and others) will almost definitely save time maintaining it.

Reference: https://kentcdodds.com/blog/write-tests by Kent C. Dodds

unittest

Included in python on version 2.1 (April 17, 2001)
Originally inspired by JUnit and has a similar flavor as major unit testing frameworks in other languages

What is pytest?

A robust Python testing tool, pytest can be used for all types and levels of software testing.
pytest can be used by development teams, QA teams, independent testing groups, individuals practicing TDD, and open source projects.

Projects all over the Internet have switched from unittest or nose to pytest, including Mozilla and Dropbox.

Why?!

What is pytest?

Offers powerful features such as:

assert rewriting
a third-party plugin model
powerful yet simple fixture model that is unmatched in any other testing framework.

Comparsion

Feature	Pytest	Unittest	Winner
Installation	Third Party	Built in	Unittest
Basic Infra	Can be only a function	Inheritance	Pytest
Basic Assertion	Builtin assert	TestCase instance methods	Pytest
Flat is better than nested	Function (1 level)	Method (2 level)	Pytest
Can run each other test	Can run unittest tests	Can't pytest test	Pytest
Test Result on console	Error Highlight, code snippet	Only line error, no highlight	Pytest
Multi param test	Yes, parametrize, keep flat	Yes, sub-test, increase nesting	Pytest
Test setup	fixture: module, session, function	Template Method: setup, tearDown	Pytest
Name Refactoring	poor, because of name conventions	rich, regular object orientation	Unittest
Running Failed Tests	built in (--lf, --ff)	your own =,(	Pytest
Marks	built in	your own =,(	Pytest

Ref: https://github.com/renzon/pytest-vs-unittest

Some useful tips

All of the tests are kept in tests and separate from the package source files in src. This isn’t a requirement of pytest, but it’s a best practice.

Brian Okken

Some useful tips

I like to keep functional and unit tests separate because functional tests should only break if we are intentionally changing functionality of the system, whereas unit tests could break during a refactoring or an implementation change.

Brian Okken