Should this be an error instead? We would not be able to run tests without Pester.

@adityapatwardhan I could change this to use Write-Error, but now I'm wondering if we should use throw instead -- after all, there is no point in continuing at all if Pester can't be found. This would terminate the script with a single error instead of several (more vague) errors.

Actually if we follow the pattern from: https://github.com/DdWr/PowerShell/blob/3fdd9f1b639df805f895c56cf574f2039ec15a76/build.psm1#L415

We should do Write-Warning and then return.

@adityapatwardhan Changes made.

A minor comment about the message -- how about this:

Write-Warning @"
Pester module not found.
Make sure that the proper git submodules are installed by running:
    git submodule update --init
"@

It looks like this:

@daxian-dbw I made the module check a little stricter here than simply checking for the path.

I actually prefer the Test-Path instead. With -ListAvailable the Pester version that comes installed with Windows 10 will be found. There are difference in those versions which might cause false errors in running tests.

@adityapatwardhan Since the full path to the project's Pester module is being passed in here, I believe this would not be an issue:

PS /Users/david/Code/PowerShell> Get-Module -ListAvailable /Users/david/Code/PowerShell/src/powershell-unix/bin/Linux/netcoreapp2.0/osx.10.12-x64/publish/Modules/Pester  | Format-Table
Path -Groupby Name

   Name: Pester

Path
----
/Users/david/Code/PowerShell/src/powershell-unix/bin/Linux/netcoreapp2.0/osx.10.12-x64/publish/Modules/Pester/Pester.psd1

However, if we only passed in Pester, I could see that being a cause for concern:

PS /Users/david/Code/PowerShell> Get-Module -ListAvailable Pester | Format-Table Path -Groupby Name
   
   Name: Pester

Path
----
/usr/local/microsoft/powershell/6.0.0-beta.8/Modules/Pester/4.0.8/Pester.psd1
/usr/local/microsoft/powershell/6.0.0-beta.8/Modules/Pester/Pester.psd1

Makes sense. Misread it being Pester instead of $Pester.