Testing and pytest

Testing

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

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