Powershell pester3/22/2023 You can also nest Describes into each other to give your test suite more structure.Ī similar keyword to Describe is Context. You can have one or more Describes per file. This keyword allows you to group tests (represented by It blocks) into groups. We can quickly look at the rest of the Pester keywords that we used. When the test was passing before, but it is not anymore, you first blame the tested function. If the test is new, and the function existed for a while, you first blame the test. What you usually do is that you look at what changed more recently. This is a bad way to break the test.īeing able to distinguish between those two is important, when your test breaks keep in mind that either the function, or the tests might be broken. The second one is when the function works correctly, but the test is incorrect. The first was that the tested function did not work correctly, this is a good way to break the test.If you look closer on how we broke the test, you can see that there are two distinct ways to break it. The error is: Expected 1, but got 8., this again reflects exactly what we did in the test, but it no longer reflects the real world. This is the output you should see in the console: To install Pester it is usually enough to just do Install-Module Pester -Force. Pester can produce artifacts such as Test Results file and can be used for generatingĬode Coverage and Test Result files for reporting Pester contains a powerful set of Mocking capabilities that allow tests to replace the behavior of anyĬommand inside of a piece of PowerShell code being tested. With Visual Studio Code, and it can of course be integrated into a build script in a CI pipeline. Pester can be run locally, where it integrates well Includes functions, Cmdlets, Modules and scripts. Pester tests can execute any command or script that is accessible to a Pester test file. Pester follows a file naming convention *.Tests.ps1, and uses a simple set of functions:ĭescribe, Context, It, Should and Mock to create a mini-DSL for writing your tests. It is also a base for tools that validate whole environments, computer deployments, database configurations and so on. Used for writing unit and integration tests, but it is not limited to just that. Pester provides a framework for writing and running tests. Pester is a testing and mocking framework for PowerShell. Building a good unit test for this requires checking both of these scenarios.Tl dr: Here is a summary. If not, Add-Content will first be called with the Path parameter passed to it, and then Get-Content will be called right afterward. If Test-Path returns $true, Get-Content will be called, and the Path parameter value will be passed to it. This function can go two different ways, depending on what Test-Path returns. If (Test-Path -Path $Path -PathType Leaf)Īdd-Content -Path $Path -Value 'something in here' Let's start with a typical function that contains some logic and a few references to other commands inside. Mocking is a way to eliminate these command dependencies and test only your code-not the code of the other commands and not code that depends on some environmental factor. So how do you build a good unit test that has calls to other commands so you can be sure it's only testing your code and not the other commands referenced? Mocking. It's best never to trust any other command in your unit test. What if the drive you placed the file on was non-existent? At the same time, you're also depending on Get-Content and Add-Content working right. In fact, it would be testing whatever storage system the file was on as well. This is not good practice as your unit test would not be testing just your code. This would test the functionality, but your unit test would then have a dependency on an environmental element (the file). You could actually put a dummy file on your system somewhere, run your code, remove the file, and run your code again. A good unit test needs to contain each of these instances to ensure the code did what you thought it would do depending on the state of the file itself. If not, you may then call Add-Content to create the file instead. For example, if you have some code that checks for the existence of a file, you might then call Get-Content to read the contents.
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