What makes a good unit test?
What is a unit test?
- trying to isolate the individual parts of the software -> units
- concerned with the functional correctness of each unit
- typically written and run by software engineers
What to test in a unit test?
- functional correctness and completeness
- error handling
- checking parameters
- correctness of return data
What defines a good unit test?
A TRIP
- Automatic
- Thorough
- Repeatable
- Independent
- Professional
automatic
- tests should be called automatic
- results of the test PASS/FAIL should be available automically
thorough
- test all key paths and scenarios
- there are coverage tools that help you with this
repeatable
- tests should produce the same outcome every time
- setup and teardown
independent & isolated
- test only one thing at a time
- when failing it should tell you the exact problem
- they should not rely on other tests (setup & teardown)
- clean up your mess
professional
- as in the production code mind good coding standards:
- test-names
- readable
AAA
- Arrange
- Act
- Assert
What does not fit in any acronym?
- keep your tests as small as possible
- prefer mock objects over setting up to much of the environment
- do not test someone else code
-
use long descriptive method name
When to write unit tests?
- try writing your tests before the code
- think of your test as a specification for your code
all or none
- write tests for all of your code and projects
- all team members must write tests
Either we all live in a decent world, or nobody does
- George Orwell
further reading
- http://stackoverflow.com/questions/61400/what-makes-a-good-unit-test
- http://www.slideshare.net/suhasreddy1/unit-testing-24134336