fix(build): target staged output for code coverage (#19)

* fix(build): target staged output for code coverage

Pester reports 0% coverage on every module scaffolded from this template
because the coverage globs point at the source tree
(`{{ModuleName}}/{Public,Private}/*.ps1`) but the test files
Import-Module from the staged build output (`Output/<Name>/<Version>/`).
Pester treats the two paths as different files, so every executed line
counts as "missed."

The natural fix — using `$Env:BHBuildOutput` directly — does not work:
PowerShellBuild only rewrites that variable to the staged version path
later, inside its own tasks. At psake `properties`-evaluation time,
`$Env:BHBuildOutput` is still BuildHelpers' default `<root>/BuildOutput`,
which doesn't exist yet and would cause Pester to bail with
"Could not resolve coverage path."

Compute the staged path explicitly from the manifest version (read via
`$Env:BHPSModuleManifest`, which BuildHelpers populates before psake
runs). This also drops the `{{ModuleName}}` placeholder from the
coverage section entirely, since the path is now derived from the
already-substituted BuildHelpers env vars.

Verified downstream in JsmOperations: Pester goes from 0% / 75% to
100% / 75% on the same test suite, with no test changes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(build): guard coverage env vars and normalize path style

Address PR #19 review feedback:

- Guard against missing $Env:BHPSModuleManifest / $Env:BHProjectName so
  bypassing build.ps1 (and Set-BuildEnvironment) fails fast with an
  actionable message instead of an obscure Import-PowerShellDataFile
  null-binding error. (Copilot review)

- Switch the staged-output assembly from Join-Path with embedded
  forward slashes to [IO.Path]::Combine to match the rest of the
  properties block and avoid mixed separators on Windows. (CodeRabbit
  review)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: tablackburn

build.psake.ps1

@@ -14,9 +14,19 @@ properties {
     $PSBPreference.Test.OutputFile = [IO.Path]::Combine($PSScriptRoot, 'out', 'testResults.xml')
     $PSBPreference.Test.OutputFormat = 'NUnitXml'
     $PSBPreference.Test.CodeCoverage.Enabled = $true
+    # Coverage must target the staged build output, not the source tree — tests
+    # Import-Module from Output/<Name>/<Version>, so Pester only records hits
+    # against those paths. $Env:BHBuildOutput points at <root>/BuildOutput at
+    # properties-evaluation time (PowerShellBuild rewrites it later inside its
+    # tasks), so we compute the staged path from the manifest version here.
+    if (-not $Env:BHPSModuleManifest -or -not $Env:BHProjectName) {
+        throw 'Coverage configuration requires BuildHelpers env vars. Run via ./build.ps1 or call Set-BuildEnvironment first.'
+    }
+    $_moduleVersion = (Import-PowerShellDataFile -Path $Env:BHPSModuleManifest).ModuleVersion
+    $_stagedOutput = [IO.Path]::Combine($PSScriptRoot, 'Output', $Env:BHProjectName, $_moduleVersion)
     $PSBPreference.Test.CodeCoverage.Files = @(
-        "$PSScriptRoot/{{ModuleName}}/Public/*.ps1"
-        "$PSScriptRoot/{{ModuleName}}/Private/*.ps1"
+        "$_stagedOutput/Public/*.ps1"
+        "$_stagedOutput/Private/*.ps1"
     )
     $PSBPreference.Test.CodeCoverage.Threshold = 0  # Threshold enforced by Codecov
     $PSBPreference.Test.CodeCoverage.OutputFile = [IO.Path]::Combine($PSScriptRoot, 'out', 'codeCoverage.xml')