Agile in a Flash 45

FIRST Properties of Unit Tests – The Code

Agile in a Flash by Jeff Langr and Tim Ottinger (card #45)

> Fast

> Isolated

> Repeatable

> Self-verifying

> Timely

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Fast. Tests should be really fast. If the entire unit test suite takes a minute, people will be reluctant to run it. Break dependencies to make tests profoundly fast and small.

Isolated. When a test fails, it should be for a single, obvious reason. A long, complex test may fail in many places for many reasons. Isolated tests can run alone or in a suite, in any order.

Repeatable. Tests can be run in a loop, without intervention. They will continue to fail or succeed until code is changed that breaks them. They do not leave the system in a state that will not allow them to run again.

Self-verifying. Unit tests are pass/fail. No interpretation is needed to determine success. If the test fails, it states why it failed.

Timely. Unit tests are written with the code, not after the code is completed. In TDD style, tests are written first. Your best results will always come from following the Red/Green/Refactor cycle.

Source: Brett Shuchert, TimOttinger

Avoid this: “I don’t have time to write tests because I am too busy debugging”

Another great blog article on this: http://blog.stevensanderson.com/2009/08/24/writing-great-unit-tests-best-and-worst-practises/