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So, to solve this issue, we can mock, replace the current implementation of New-Item with our own. More likely, you just want to see the test does what it's supposed to, i.e. As part of testing, you don't want it to create a file each time the test is being run. Your code is calling New-Item, which creates a new file. Ok, so you have added Save-Tomato() to your script file. Dot source the code to ensure it's being picked up:.

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Update the Get-Tomato.ps1 file with this code:.

So, in this case, imagine that our production code now will have more function Save-Tomato that saves an object to a file. All you need to do is to focus that the right behavior happens. The short answer is that you can use mocks, a construct that's executed instead of the actual command. Let's look at such a case and how Pester handles it. You will have code that you write that eventually performs side effects, like accessing a network resource or create a file. Great, you ran a test on a more real looking code. Tests Passed: 1, Failed: 0, Skipped: 0 NotRun: 0

To run the test, call Invoke-Pester (./ for the path in Linux ans macOS and.

Note the use of the Should -Be, which determines equality between $Value and 'Value'. Within the test, there's test itself where the code is set up: Within the suite there's a test definition It, which also has a string argument that represents the name of the test. The test above, have a Describe construct which is the declaration of a suite, and a string argument, giving the suite a name.

To create our first test, create a file A-Test.ps1.

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Pester 3 comes pre-installed with Windows 10 Our first testįor our first test, we will learn how to write a test as well as running it. It is compatible with Windows PowerShell 3, 4, 5, 6 and 7. Pester runs on Windows, Linux, MacOS and anywhere else thanks to PowerShell. Once it's installed, you can start authoring your tests.

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To install Pester, you run the below command. When you want your tests to focus on the behavior on the tests, mocking is a good idea. In you tests you might have calls to commands that carry out side-effects, like accessing a data store or creating a file for example. When you start having quite a few tests, you want a way to group those tests into larger logical groups, that's what test suites are. You can run tests with Pester, both a single test with a single piece of input as well as testing many different inputs at once. Pester comes with diverse ways of asserting conditions that will determine if your tests should fail or not. Pester is a test framework meant for PowerShell and is a module you can install. There are many other reasons for wanting to have tests but the three above are quite compelling.

If you create tests around what you do, you ensure you build your code in a way that makes it testable. Another reason for having tests is that it drives architecture. With this confidence you start daring to change this, if you for example would need to refactor code and ensure it still works after those changes. When you have a lot of tests covering your code it creates a level of confidence. Ensure your code works as as intended for certain scenarios. The reason you want to have tests are many: TLDR this article covers the testing framework Pester that you use to test your PowerShell scripts.