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You write your tests “in” Pester and Pester runs your tests for you. It’s an automated unit-testing framework for PowerShell.

PESTER POWERSHELL WINDOWS 10

Pester (“PowerShell Tester,” sort of) is an open-source project which is bundled with Windows 10 and later (although newer versions can be found in the PowerShell Gallery). If you did a good job on the tests themselves, then you’ll know your feature is working correctly. But then you start coding the new feature, and you keep coding until all the tests pass. Initially, the tests will fail, because you haven’t coded up the new feature yet. Those tests would describe how you want the new feature to work, and they serve as a kind of functional specification. Rather than breaking out the command’s script and starting to modify it, you’d first write a few tests to test the proposed new feature. Let’s say you decide to add a new feature to a command. Even if someone else modifies your script, and they didn’t know about that weird condition, the automated test will still have their back, and make sure the weird condition gets tested.Īutomated testing can even move you to a world of Test-Driven Development (TDD).

Automated tests, therefore, serve as a kind of documented institutional memory.

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Also, because it learns – if you run across some weird condition that broke your code one time, you add a test for that condition to your test script, and then you’ll never “forget” to test that weird condition again. Remember, PowerShell is all about automation – why should testing be excluded from that?Īutomated testing, on the other hand, rocks.

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You can’t achieve The Miracle with manual testing. It’s not like you have a huge list of tests which you know you need to run through you’re probably doing what we do and thinking, “well, I’ll run it with parameters one time, pipe some stuff to it another time, and this is probably good.” If you fix a problem, you might test that specific problem right then, but you might or might not re-test that specific problem in the future. Even if you’re not flat-out lazy, manual testing takes time and effort that could be better spent elsewhere. And it’ll always be the one test you didn’t run that would have caught the error in your code. You’re not going to run every possible test every time through. But there are some real problems with manual testing: And this is fine – you should definitely test your code as you go.

We’re sure that you’ve manually tested your scripts before – possibly even as you wrote scripts for this book. That way, any time you revise your code, The Miracle can quickly re-test it, make sure it’s working, and deploy it – or bounce it back to you for fixes. But the bit you need to contribute to The Miracle is a way of automatically testing your code. Step number three is what we call The Miracle, as in, “you check in your code, The Miracle occurs, and your code is deployed.” Step three is entirely automated – and every tool you need to make step three happen exists today. If the tests pass, your code is deployed to a deployment repository (maybe, or maybe a private repo), making it available for production.If the tests fail, you get an email telling you what happened. The pipeline copies your script into the virtual machine, and runs several automated tests.

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Usually incorporating third-party tools (TeamCity is the one used on ’s free build service, for example), the pipeline builds out a virtual machine to test your script. The repository triggers a continuous integration pipeline.You check your code into a source control repository.You write up some code, or modify some old code.Or, you might find some odd condition under which your script fails – well, you certainly don’t want to forget to test that condition again in the future, do you? And although you might run a few tests on your script, you – or someone else – might also modify your script at some point, necessitating a re-test. Here’s the deal: nobody likes a broken script in production. Just enter code fccjones into the discount code box at checkout at .Īs we move into a DevOps-y world, one of the things you’ll need to start thinking about is how you’ll test your scripts. Save 37% on Learn PowerShell Scripting in a Month of Lunches.

In this article, we’ll talk about automated unit testing for PowerShell scripts.

From Learn PowerShell Scripting in a Month of Lunches by Don Jones and Jeffery Hicks

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