test: add Build-PSBuildMAMLHelp integration coverage

tests/Build-PSBuildMAMLHelp.tests.ps1

@@ -0,0 +1,48 @@
+Describe 'Build-PSBuildMAMLHelp' {
+  BeforeAll {
+    $script:moduleName = 'PowerShellBuild'
+    $script:moduleRoot = Split-Path -Path $PSScriptRoot -Parent
+    Import-Module ([IO.Path]::Combine($script:moduleRoot, 'Output', $script:moduleName)) -Force
+  }
+
+  It 'Generates help for each locale directory under Path' {
+    Mock Get-ChildItem {
+      @(
+        [PSCustomObject]@{ Name = 'en-US' }
+        [PSCustomObject]@{ Name = 'fr-FR' }
+      )
+    } -ParameterFilter { $Path -eq 'docs/help' -and $Directory }
+
+    Mock New-ExternalHelp {}
+
+    Build-PSBuildMAMLHelp -Path 'docs/help' -DestinationPath 'out/module' -Verbose:$false
+
+    Assert-MockCalled New-ExternalHelp -Times 2 -Exactly
+    Assert-MockCalled New-ExternalHelp -Times 1 -Exactly -ParameterFilter {
+      $Path -eq [IO.Path]::Combine('docs/help', 'en-US') -and
+      $OutputPath -eq [IO.Path]::Combine('out/module', 'en-US') -and
+      $Force -eq $true -and
+      $ErrorAction -eq 'SilentlyContinue'
+    }
+    Assert-MockCalled New-ExternalHelp -Times 1 -Exactly -ParameterFilter {
+      $Path -eq [IO.Path]::Combine('docs/help', 'fr-FR') -and
+      $OutputPath -eq [IO.Path]::Combine('out/module', 'fr-FR') -and
+      $Force -eq $true -and
+      $ErrorAction -eq 'SilentlyContinue'
+    }
+  }
+
+  It 'Surfaces errors from New-ExternalHelp (platyPS dependency)' {
+    Mock Get-ChildItem {
+      @([PSCustomObject]@{ Name = 'en-US' })
+    } -ParameterFilter { $Path -eq 'docs/help' -and $Directory }
+
+    Mock New-ExternalHelp {
+      throw 'The term New-ExternalHelp is not recognized as the name of a cmdlet.'
+    }
+
+    {
+      Build-PSBuildMAMLHelp -Path 'docs/help' -DestinationPath 'out/module' -Verbose:$false
+    } | Should -Throw '*New-ExternalHelp*'
+  }
+}