Gets a list of changed files in a given repository directory and runs tests that match them.

Invoke-ModifiedTests.ps1

function Invoke-ModifiedTests {
    <#
        .Synopsis
            Gets a list of changed files in a repository, and run every changed test and test matching a changed function/file

        .Description
            This assumes that each file has a matching .Tests.ps1 file, suited for running with Pester. It also ignores Integration tagged tests.

        .Example
            Invoke-ModifiedTests -Repository C:\Source\Module

            # Runs modified tests and modified-function tests within C:\Source\Module
    #>
    param(
        # Path to the repository to test
        [ValidateScript({
            if (-not (Test-Path (Join-Path $_ '.git') -Type Container)) {
                throw "Directory should be a Git repository"
            }
            $true
        })]
        [Alias('PSPath')]
        [string]$Repository,

        # If provided, will not search for tests matching non-test files
        [switch]$IgnoreChangedFunctions
    )
    process {
        Push-Location $Repository
        $ChangedFiles = git diff master... --name-only | Convert-Path

        $ChangedTests = $ChangedFiles.Where{$_.EndsWith('.Tests.ps1')}
        $ChangedFunctions = $ChangedFiles.Where{$_ -notmatch ".Tests.ps1$" -and $_.EndsWith('.ps1')}

        Write-Host "$($ChangedTests.Count) tests have been modified. $($ChangedFunctions.Count) have been modified."
        if (-not $IgnoreChangedFunctions) {
            foreach ($Function in $ChangedFunctions) {
                $TestFound = $false

                $ChangedTests += (Get-ChildItem -Filter "$(([IO.FileInfo]$Function).BaseName).Tests.ps1" -Recurse -OutVariable TestFound).FullName

                if (-not $TestFound) {
                    Write-Warning "No tests found for $($Function.Name)!"
                }
            }
        }

        Invoke-Pester -Script $ChangedTests -ExcludeTag Integration
        Pop-Location
    }
}