Write Meaningful Error Messages in Automated Tests

Here’s a tip: Write your automated tests with the failure in mind. Especially, consider a future maintainer who may need a useful error message. 

This can help when the test fails in the future (and it probably will). A descriptive message helps understand the technical issue you’re looking at and will ideally guide you to finding a solution.

Let’s look at some examples that leave something to be desired. These messages may be true, but don’t help to understand the underlying problem:

• Expected true, but got false
• The result message is malformed
• fail

Yes, I have seen these or very similar messages, that are rather useless. 

Imagine how much more helpful, the following messages are:

• Expected condition XY to be true in context AB of object O
• The message ‘<output the actual message>’, is malformed and cannot be processed further
• Got <actual result> instead of <expected_result> when processing XY

These improved messages can guide you, help you remember the context and figure out the underlying issue when the test fails.

I find that this improvement shortens the time spent with failure analysis. It makes my days more productive because I get a message that tells me about the context where thing went wrong. 

Do you have similar ideas about how to improve (automated) tests?
I’d love to hear about them.