test: add pester tests

.github/workflows/test.yml

@@ -32,12 +32,12 @@ jobs:
         run: |
           $expected = (Join-Path $pwd test stubs expected replaced.tpl)
           $subject = (Join-Path $pwd test subject-${{ matrix.style }}.tpl)
-          $prestine = (Join-Path $pwd test stubs prestine ${{ matrix.style }}.tpl)
+          $pristine = (Join-Path $pwd test stubs pristine ${{ matrix.style }}.tpl)
 
           $untouched = (Join-Path $pwd test stubs untouched no-matches.tpl)
           $untouchedHash = (Get-FileHash -Path $untouched -Algorithm SHA256).Hash
 
-          Copy-Item -Path $prestine -Destination $subject
+          Copy-Item -Path $pristine -Destination $subject
 
           Write-Output "expected-path=$expected" | Out-File -FilePath $env:GITHUB_OUTPUT -Encoding utf8NoBOM -Append
           Write-Output "subject-path=$subject" | Out-File -FilePath $env:GITHUB_OUTPUT -Encoding utf8NoBOM -Append
@@ -104,3 +104,15 @@ jobs:
           } else {
             echo "✓ Token untouched test passed"
           }
+
+  pester:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@main
+
+      - name: Run Pester Tests
+        shell: pwsh
+        run: |
+          $testPath = (Join-Path -Path "$env:GITHUB_WORKSPACE" -ChildPath 'test')
+          Invoke-Pester -Path (Join-Path -Path $testPath -ChildPath 'ReplaceTokens.Tests.ps1') -Output Detailed

.gitignore

@@ -118,3 +118,5 @@ scratch.*
 # !.vscode/launch.json
 # !.vscode/settings.json
 # !.vscode/tasks.json
+
+test/TokenReplaceTest/

test/ReplaceTokens.Tests.ps1

@@ -0,0 +1,88 @@
+# Usage: Invoke-Pester -Path ReplaceTokens.Tests.ps1 -Output Detailed
+
+# Check if Pester is installed, if not, install it
+if (-not (Get-Module -Name Pester -ListAvailable))
+{
+    Install-Module -Name Pester -Force -SkipPublisherCheck
+}
+
+# Import the script being tested
+$scriptPath = Join-Path -Path (Get-Item -Path $PSScriptRoot).Parent.FullName -ChildPath 'action.ps1'
+
+Describe 'ReplaceTokens Function' {
+
+    BeforeAll {
+        # Set up a temporary test directory
+        $testDir = Join-Path -Path $PSScriptRoot -ChildPath 'TokenReplaceTest'
+        New-Item -Path $testDir -ItemType Directory -Force | Out-Null
+    }
+
+    AfterAll {
+        # Cleanup test directory
+        Remove-Item -Path $testDir -Recurse -Force
+    }
+
+    It 'Checks the script path' {
+        # Act
+        $scriptPath = Join-Path -Path (Get-Item -Path $PSScriptRoot).Parent.FullName -ChildPath 'action.ps1'
+
+        # Assert
+        $scriptPath | Should -Not -BeNullOrEmpty
+        $scriptPath | Should -BeExactly (Join-Path -Path (Get-Item -Path $PSScriptRoot).Parent.FullName -ChildPath 'action.ps1')
+    }
+
+    It 'Replaces tokens when environment variables exist' {
+        # Arrange
+        $testFile = Join-Path -Path $testDir -ChildPath 'test1.txt'
+        Set-Content -Path $testFile -Value 'Hello, {{NAME}}!' -Encoding utf8NoBOM -NoNewline
+
+        $env:NAME = 'Alice'
+
+        # Act
+        & $scriptPath -Path $testFile -Style 'mustache' -Encoding 'utf8NoBOM' -NoNewline
+        $result = Get-Content -Path $testFile -Raw
+
+        # Assert
+        $result | Should -Be 'Hello, Alice!'
+    }
+
+    It 'Does not replace tokens if no matching environment variable exists' {
+        # Arrange
+        $testFile = Join-Path -Path $testDir -ChildPath 'test2.txt'
+        Set-Content -Path $testFile -Value 'Welcome, {{REPLACE_TOKENS_ACTION}}!' -Encoding utf8NoBOM -NoNewline
+
+        # Act
+        & $scriptPath -Path $testFile -Style 'mustache' -Encoding 'utf8NoBOM' -NoNewline
+        $result = Get-Content -Path $testFile -Raw
+
+        # Assert
+        $result | Should -Be 'Welcome, {{REPLACE_TOKENS_ACTION}}!' # Token remains unchanged
+    }
+
+    It 'Handles empty environment variable values correctly' {
+        # Arrange
+        $testFile = Join-Path -Path $testDir -ChildPath 'test3.txt'
+        Set-Content -Path $testFile -Value 'Your ID: {{ID}}' -Encoding utf8NoBOM -NoNewline
+
+        $env:ID = ''
+
+        # Act
+        & $scriptPath -Path $testFile -Style 'mustache' -Encoding 'utf8NoBOM' -NoNewline
+        $result = Get-Content -Path $testFile -Raw
+
+        # Assert
+        $result | Should -Be 'Your ID: {{ID}}' # Should remain unchanged with a warning
+    }
+
+    It 'Applies correct encoding options' {
+        # Arrange
+        $testFile = Join-Path -Path $testDir -ChildPath 'test5.txt'
+        Set-Content -Path $testFile -Value 'Encoding Test' -Encoding ascii -NoNewline
+
+        # Act
+        $result = Get-Content -Path $testFile -Raw -Encoding ascii
+
+        # Assert
+        $result | Should -Be 'Encoding Test'
+    }
+}