test: Add Clear-PSBuildOutputFolder coverage

tests/Clear-PSBuildOutputFolder.tests.ps1

@@ -0,0 +1,33 @@
+Describe 'Clear-PSBuildOutputFolder' {
+
+    BeforeAll {
+        $script:moduleRoot = Split-Path -Path $PSScriptRoot -Parent
+        Import-Module -Name ([IO.Path]::Combine($script:moduleRoot, 'Output', 'PowerShellBuild')) -Force
+    }
+
+    It 'removes the output folder when it exists' {
+        $outputPath = Join-Path -Path $TestDrive -ChildPath 'Output'
+        $nestedPath = Join-Path -Path $outputPath -ChildPath 'Nested'
+        $nestedFilePath = Join-Path -Path $nestedPath -ChildPath 'marker.txt'
+        New-Item -Path $outputPath -ItemType Directory -Force > $null
+        New-Item -Path $nestedPath -ItemType Directory -Force > $null
+        New-Item -Path $nestedFilePath -ItemType File -Force > $null
+
+        Clear-PSBuildOutputFolder -Path $outputPath
+
+        Test-Path -Path $outputPath | Should -BeFalse
+    }
+
+    It 'refuses a path short enough to be a drive root' {
+        Mock -CommandName 'Test-Path' -ModuleName 'PowerShellBuild' -MockWith { $false }
+
+        { Clear-PSBuildOutputFolder -Path 'C:\' } |
+            Should -Throw -ExpectedMessage '*must be longer than 3 characters.*'
+    }
+
+    It 'does not throw when the output folder does not exist' {
+        $outputPath = Join-Path -Path $TestDrive -ChildPath 'MissingOutput'
+
+        { Clear-PSBuildOutputFolder -Path $outputPath } | Should -Not -Throw
+    }
+}