Currently there is no way of telling whether a PowerShell Script (.ps1) is full of pester (or perhaps Gherkin) tests or if it is an actual script without adding .tests. in between the file name and the ps1 extension

This would make it cleaner in visibility as currently you could have the following

Install-MyModule.ps1
MyModule.psd1
MyModule.psm1
MyModule.psm1-help.xml

And then the tests files could be the following
MyModule.Tests.ps1
Import-MyModule.Tests.ps1

To combat this I would propose that tests could be formed in a file with a pst1 extension