Invoke-Pester -Parallel

[DarkLite1]

I've read somewhere that the Pester 6 supports running tests in parallel? That would be of great help to speed up testing when multiple .Tests.ps1 files are present. Something like Invoke-Pester -Parallel.

[nohwnd]

https://pester.dev/docs/usage/parallel yes that is true, in 6.1.0 (coming soon, preview is already there) it is even better. Is your idea that we should add that -Parallel top level switch, or is this a general question if Parallel is available?

[DarkLite1]

I would expect Pester to run in parallel whenever possible (by default), so a switch would not be needed. But when that yields issues, it might be good to have an option to disable parallel for troubleshooting.

I'm going to love this new feature, thank you. We currently have tests taking 5 tot 10 minutes. This would be a game changer.

[fflaten]

Looking forward to feedback and/or bug reports 🙂

I would expect Pester to run in parallel whenever possible (by default), so a switch would not be needed.

Running in parallel is still experimental and not fully tested for all features. More importantly, debugging does not work out of the box. Too complicated across threads.

So better to keep this opt-in for those who want the performance, while running and debugging just works by default. Maybe that changes in the future (v7?) if tooling and docs are better - only time will tell.

[DarkLite1]

I fully understand this to be opt-in for now. Thank you for clarifying. The thing is, I only use Pester-Invoke without a config file when I'm testing my code. In that case a switch like Invoke-Pester -Parallel -ThrottleLimit 5 would be helpful. Just a thought.

In our script you can see that executing Invoke-Pester takes 5 minutes. For working with parallelism in this script I've written the function Invoke-WithOptionalParallelismHC, this can be useful for Pester too. When you set -ThrottleLimit 1, parallelism is avoided and you can simply step through the code. If it's higher you have parallelism on the same code.

Another tip I would like to give, with regards to parallelism and runspaces, is to use DTO's instead of the $using: variable. It's much more reliable and easier to debug. For an example check line 166 in this file. You simply flatten the objects and use them as arguments.

You guys are probably a lot smarter than me and it took me a while to figure this pattern out, but I just though that sharing might help in case you haven't seen this pattern before.

One other issue I have with running this code with Invoke-Pester is that the end result, the summary in the end, is not always visible. This depends on the height of the terminal. When I set the height of the terminal "window maximized" in VS Code Studio on the integrated Windows PowerShell Extension, we always see the colored summary at the end. If not maximized, it's possible we just see a black space and no summary. While executing, we see many "Remove file .... " messages, that are a bit meaningless at that point.

Thanks again for the amazing code. We use it every day.