Rock-Solid PowerShell Projects

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We write a lot of PowerShell. We didn’t realize it when we started, but our projects have gotten much bigger. What seemed like a small bit of glue scripting is now the core project. As the projects grew we learnt some lessons in how to keep them maintainable.

Our first release was really simple. It was just enough to meet our project goals. We didn’t think through how the different pieces would fit together. Fast forward 2 years and the older projects felt very thrown together.

When we started a new project I wanted to make it feel like a professional software project. Instead of the good enough we had with the first project, I wanted everything to fit together just right. I want to apply all the best practices we use with any other development. Just being glue was not enough.

This list might seem straightforward and mundane. That is okay! I think these guidelines are essential for any project worth your time to maintain. With a looser language like PowerShell, these conventions helped give our new project even more structure. Ultimately, they led to better code we can all understand.

Consistent Layout

At first, we tossed our files in one big directory and a bunch of messy dot sourced files. This was brutal. Finding anything was impossible.

Now we have all entry scripts at the root of the project, all modules in a lib folder and tests on their own. More folders are added as needed. A consistent layout for files makes it easy to find your way around.

We took this even further. We applied the same basic layout to all the projects and libraries we maintain. Every repository now includes a build file, release notes and a in addition to consistent directories. New developers (or you after 4 months away) can open any project and start contributing right away.

Test Thoroughly

We were naive when we started our first project. What the project did was really simple. As a result, we thought all we needed to do was run the code once through the happy path. As the code grew this was no longer enough.

We now diligently test each module independently using Pester then again with more comprehensive integration tests together. Pester is an amazing testing library for PowerShell. We love Pester. If you have not used it, go check it out now.

Pester has greatly improved our unit testing. Our previous testing only validated large scenarios and missed the edge cases. We now test individual functions in isolation to expose more permutations caused by the lower levels.

Modules for Everything

Initially, any reusable functions were placed in magical library.ps1 scripts, which would be dot sourced in every other script (i.e. . $PsDir\library.ps1 everywhere, boo). Everything was written as a script to either be dot sourced or directly called. This was great when we started but did not scale as the project became more complex.

With newer projects we place everything into independent modules. Each module has a single responsibility, i.e. setting up part of our application. This keeps every module small and focused.

Within each module, we intentionally keep some functions private. This allows us to shrink the module’s surface area without losing functionality. With our included scripts this would not have been possible.

Mandatory Continuous Integration

From the beginning, our projects have had the ability to check them out, run all tests and publish releases. This allowed us to rapidly add functionality while keeping up our basic hygiene. The code remains clean and we can make sure it always meets our basic requirements.

As we continued to improve, most of our projects have added Preflights. This complemented our existing continuous integration. Now we stop problems from ever reaching our master branch.

Our added emphasis on testing at various levels has improved our confidence. Every build/test run covers even more of the application and edge cases.


We have learnt a lot from maintaining PowerShell projects over the past few years. Our new projects are rock-solid. We try to have the following in every project:

  • Consistent Layout
  • Thorough Testing
  • Single Responsibility Modules
  • Continuous Integration

This has made our projects easier to understand and update.

Have your glue scripts turned into something bigger? Is it time to take it to the next level?

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