SMART Tests Outwit Bugs

With the new year come the typical thoughts of goals and resolutions.  I have come across the SMART acronym many times.  It states that goals should be:

Specific
Measurable
Attainable
Reasonable
Timely

After some thought, I realized that this also applies to tests.

Specific - A test should target one specific feature or behavior. The name of the test should be representative of what that behavior or feature is. When I name my tests in this way, as soon as the test failure is seen, I know what's broken. By looking at a few lines of code, I should know where the cause of the failure is. If I can't tell by looking at the code, my test is not specific enough. This also relates to the one (conceptual) assert per test idea. Like the high-contrast target above, you want to be able to tell, instantly, what went wrong.

Measurable - If you can't measure what you're attempting to test, it's pointless. For example, I don't test that the screen is drawn pixel perfect. It's not easily measurable. To attempt to test it would be a waste of my time. Manual tests are still tests; use them. TDD isn't a panacea.

Accurate - I consider a test accurate if it meets two requirements. First, it's name must represent the behavior being tested. Second, I must be able to look at the test and very quickly ascertain that it does what it says it does. Uncle Bob Martin's book, Clean Code, describes a good function as one that has a single abstraction -- one that can't be refactored any further.

Responsible - I shouldn't have to say this, but tests should NOT have side-effects. Tests with side-effects destroy any confidence that a later test may, or may not, be correct. Don't write tests with side effects.

Timely - Long-running tests are less-run tests. If a test isn't fast, I'm not going to run it as often. And, when I do run it, I'm likely to get distracted and start answering lots of Stack Overflow questions while I'm waiting for it to run.

Write SMART tests. By doing so, it becomes much easier to outwit bugs.

[Image from: http://www.ctc.com.pt/fotos_20061007.html]