The goal of testing in PowerShell is to ensure that code works as it has been designed. Automatic testing ensures that this continues to be the case as code is changed over time.

Testing often begins before code is ready to execute. PSScriptAnalyzer can look at code and provide advice on best practices. This technique is known as static analysis.

Unit tests pick up when code is ready to execute. Tests may exist before the code when following practices such as Test-Driven Development (TDD). A unit test focuses on the smallest parts of a script, function, module, or class. A unit test strives to validate the inner workings of a unit of code, ensuring that conditions evaluate correctly, that it terminates or returns where it should, and so on.

Testing might extend into systems and acceptance testing, although this often requires a test environment to act against. Acceptance testing may include black-box testing, used to verify that a command accepts known parameters and generates an expected set of results. Black-box testing, as the name suggests, does not concern itself with understanding how a block of code arrives at a result.

The following topics are covered in this chapter:

• Static analysis
• Testing with Pester