Finding patterns of failure in a Unit Test
- by Pekka
I'm new to Unit Testing, and I'm only getting into the routine of building test suites. I have what is going to be a rather large project that I want to build tests for from the start.
I'm trying to figure out general strategies and patterns for building test suites. When you look at a class, many tests come to you obviously due to the nature of the class. Say for a "user account" class with basic CRUD operations, being related to a database table, we will want to test - well, the CRUD.
creating an object and seeing whether it exists
query its properties
change some properties
change some properties to incorrect values
and delete it again.
As for how to break things, there are "fail" tests common to most CRUD classes like:
Invalid input data types
A number as the ID key that exceeds the range of the chosen data type
Input in an incorrect character encoding
Input that is too long
And so on and so on.
For a unit test concerned with file operations, the list of "breaking things" could be
Invalid characters in file name
File name too long
File name uses incorrect protocol or path
I'm pretty sure similar patterns - applicable beyond the unit test one is currently working on - can be found for most units that are being tested.
Now my question is:
Am I correct in seeing such "breaking patterns"? Or am I getting something completely wrong about Unit testing, and if I did it right, this wouldn't be an issue at all? Is Unit Testing as a process of finding as many ways to break the unit as possible the right way to go?
If I am correct: Are there existing definitions, lists, cheat sheets for such patterns?
Are there any provisions (mainly in PHPUnit, as that's the framework I'm working in) to automate such patterns?
Is there any assistance - in the form of check lists, or software - to aid in writing complete tests?
