Spock: Up and Running

Chapter 3. Spock Assertions

In Chapter 2, you learned that any Boolean expression in a then: block or expect: block is treated as an assertion. In this chapter, we examine assertions in depth. You will learn about various techniques for writing concise and expressive assertions using Groovy’s enhancements to the core Java APIs. We also discuss the importance of good diagnostics in your Spock specifications and how to structure assertions to provide the most information in case of a failure.

I have three goals when writing assertions in tests. Listed most important first, they are:

Good diagnostics

If the assertion fails I should be able to see very easily in the test report what exactly is wrong. I don’t want a generic exception or a poorly worded message that doesn’t really tell me anything beyond “something is wrong.”

Expressiveness

When I look at the test, I want to be able to see right away what is being asserted without having to scratch my head over convoluted code. When I introduce a regression, I want to be able to determine whether the test I have broken is still valid or is now obsolete due to the change I am implementing.

Conciseness

This is related to expressiveness in that the shorter a piece of code is, the easier it is to read. However, there’s a point beyond which brevity comes at the cost of comprehensibility. Short is good but not when it begins to resemble an obfuscated code contest entry!

The Importance of Good Diagnostics

If you’ve practiced or read ...