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GNU Smalltalk User's Guide

2.7.4.1 Where should you start?

Testing is one of those impossible tasks. You'd like to be absolutely complete, so you can be sure the software will work. On the other hand, the number of possible states of your program is so large that you can't possibly test all combinations.

If you start with a vague idea of what you'll be testing, you'll never get started. Far better to start with a single configuration whose behavior is predictable. As you get more experience with your software, you will be able to add to the list of configurations.

Such a configuration is called a fixture. Two example fixtures for testing Floats can be 1.0 and 2.0; two fixtures for testing Arrays can be #() and #(1 2 3).

By choosing a fixture you are saying what you will and won't test for. A complete set of tests for a community of objects will have many fixtures, each of which will be tested many ways.

To design a test fixture you have to

• Subclass TestCase
• Add an instance variable for each known object in the fixture
• Override setUp to initialize the variables