Test One Concept at a Time
Are there multiple tests? Does each test have a clear goal?
Each of your tests should prove one, and only one, specific behavior about the target class.
Elsewhere this documentation discussed the problem with tests like System.assert(x != null). This test was too broad: it would pass when x took on almost any value. An example refactored this test into a more specific version.
Successful test classes will include multiple specific tests like the one demonstrated above. Each test method will pick a concept and test the target method against that concept. See here for examples of specific concepts. Separating each concept into its own method, with a descriptive name, creates a readable, maintainable test class.
By separating test methods from each other, it's much easier to see when you are covering the entire target class and taking different inputs into account.
You know you have a one-concept test when:
- You can give the test method a clear name (if the name contains the word 'and', you may have a problem!)
- Your test contains a single assertion or a small number of assertions testing related information.
To receive credit for this objective:
- The test class has multiple methods.
- Each test method proves one, and only one, specific behavior about the target class.