The build script is totally hosed ...

[Jaykul]

1. First it doesn't [CmdletBinding()] ....
2. Then, it tries to -ForceBootstrap on NuGet (without -Scope) which requires elevation
3. Then, it tries to install some modules with -Force, meaning it installs them every time
4. Then it installs some other modules without -Scope, meaning it has to be elevated
5. Then it doesn't explicitly import Pester 4, meaning all the tests fail
6. But worse, the built module won't work, because it's missing the initialization code which only exists in PSSlack.psm1

Of course, it turns out you're not using the build anyway, you're just shipping the source!

I would suggest using Install-RequiredModule, or maybe PSDepends 😉, and stick that initialization code into a private folder somewhere...