ci: run the tests weekly on the Windows emulator

.github/scripts/windows/install-cosmos-emulator.ps1

@@ -1,20 +1,21 @@
+# Installs the Windows Azure Cosmos DB Emulator unless it is installed already, as it is on the hosted Windows runners.
+# Fails when the installation fails.
 $emulatorPath = Join-Path $env:ProgramFiles 'Azure Cosmos DB Emulator\CosmosDB.Emulator.exe'
 if (Test-Path $emulatorPath) {
-	"installed=true" >> $env:GITHUB_OUTPUT
 	Write-Host 'Azure Cosmos DB Emulator is already installed.'
 	exit 0
 }
 
 choco install azure-cosmosdb-emulator -y --no-progress --install-arguments="'/l*v C:\azure-cosmosdb-emulator_msi_install.log'"
 if ($LASTEXITCODE -eq 0 -and (Test-Path $emulatorPath)) {
-	"installed=true" >> $env:GITHUB_OUTPUT
 	Write-Host 'Azure Cosmos DB Emulator installed successfully.'
+	exit 0
 }
-else {
-	"installed=false" >> $env:GITHUB_OUTPUT
-	Write-Warning 'Azure Cosmos DB Emulator installation failed. Continuing because Windows job runs build-only target.'
-	if (Test-Path 'C:\azure-cosmosdb-emulator_msi_install.log') {
-		Write-Host 'MSI log tail:'
-		Get-Content 'C:\azure-cosmosdb-emulator_msi_install.log' -Tail 120
-	}
+
+if (Test-Path 'C:\azure-cosmosdb-emulator_msi_install.log') {
+	Write-Host 'MSI log tail:'
+	Get-Content 'C:\azure-cosmosdb-emulator_msi_install.log' -Tail 120
 }
+
+Write-Error 'Azure Cosmos DB Emulator installation failed.'
+exit 1

.github/scripts/windows/start-cosmos-emulator.ps1

@@ -1,25 +1,20 @@
-$emulatorPath = Join-Path $env:ProgramFiles 'Azure Cosmos DB Emulator\CosmosDB.Emulator.exe'
-Start-Process -FilePath $emulatorPath -ArgumentList '/NoUI /NoExplorer /AllowNetworkAccess /EnablePreview' -PassThru | Out-Null
+# Starts the installed Windows Azure Cosmos DB Emulator through its PowerShell module, as the emulator's documentation
+# shows for GitHub Actions, and fails unless the emulator then answers on https://127.0.0.1:8081.
+# /AllowNetworkAccess is not passed: it requires /Key or /KeyFile as well, and without one the emulator never became
+# ready on the hosted runners. The tests reach the emulator on the local host anyway.
+$ErrorActionPreference = 'Stop'
 
-$maxAttempts = 60
-for ($attempt = 1; $attempt -le $maxAttempts; $attempt++) {
-	try {
-		# An unauthenticated request to the emulator root returns 401 once it is up.
-		# PowerShell 7 throws for 4xx responses unless -SkipHttpErrorCheck is set.
-		$response = Invoke-WebRequest -Uri 'https://127.0.0.1:8081/' -SkipCertificateCheck -SkipHttpErrorCheck -Method Get -TimeoutSec 5
-		if ($response.StatusCode -in 200, 401) {
-			Write-Host "Cosmos DB Emulator is ready on Windows (status: $($response.StatusCode))."
-			exit 0
-		}
+Import-Module (Join-Path $env:ProgramFiles 'Azure Cosmos DB Emulator\PSModules\Microsoft.Azure.CosmosDB.Emulator')
 
-		Write-Host "Cosmos DB Emulator returned status $($response.StatusCode) (attempt $attempt/$maxAttempts)."
-	}
-	catch {
-		Write-Host "Cosmos DB Emulator is not ready yet (attempt $attempt/$maxAttempts)."
-	}
+# Waits until the emulator accepts requests. Its first start on a fresh runner initialises the data directory, which
+# takes several minutes.
+Start-CosmosDbEmulator -NoUI -EnablePreview -Timeout 900
 
-	Start-Sleep -Seconds 5
+# An unauthenticated request to the emulator root returns 401 once it is up.
+# PowerShell 7 throws for 4xx responses unless -SkipHttpErrorCheck is set.
+$response = Invoke-WebRequest -Uri 'https://127.0.0.1:8081/' -SkipCertificateCheck -SkipHttpErrorCheck -Method Get -TimeoutSec 30
+if ($response.StatusCode -notin 200, 401) {
+	throw "Cosmos DB Emulator answered with status $($response.StatusCode) after it started."
 }
 
-# Warn instead of failing: the Windows job runs the build-only target, so it does not need the emulator.
-Write-Warning 'Cosmos DB Emulator failed to become ready on Windows. Continuing because Windows job runs build-only target.'
+Write-Host "Cosmos DB Emulator is ready on Windows (status: $($response.StatusCode))."

.github/workflows/build.yml

@@ -25,18 +25,6 @@ jobs:
           dotnet-version: |
             10.x
 
-      - name: Install Azure Cosmos DB Emulator (Windows)
-        id: install_cosmos_windows
-        if: runner.os == 'Windows'
-        shell: pwsh
-        run: ./.github/scripts/windows/install-cosmos-emulator.ps1
-        continue-on-error: true
-
-      - name: Start Azure Cosmos DB Emulator (Windows)
-        if: runner.os == 'Windows' && steps.install_cosmos_windows.outputs.installed == 'true'
-        shell: pwsh
-        run: ./.github/scripts/windows/start-cosmos-emulator.ps1
-
       - name: Start Azure Cosmos DB Emulator container
         if: runner.os == 'Linux'
         run: bash ./.github/scripts/linux/start-cosmos-emulator.sh

.github/workflows/windows-emulator-weekly.yml

@@ -0,0 +1,52 @@
+name: Windows emulator weekly
+
+# Runs every test against the Windows emulator. The workflow of a pull request runs them on the Linux vNext emulator
+# only, and the two emulators answer some queries differently, so this lane checks the expectations the tests state
+# for the Windows emulator. It runs once a week, early on Monday, and on demand, and on a pull request only when the
+# pull request changes this lane, so it never holds up other pull requests.
+on:
+  schedule:
+    - cron: '23 2 * * 1'
+  workflow_dispatch:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - .github/workflows/windows-emulator-weekly.yml
+      - .github/scripts/windows/**
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        configuration: [Debug, Release]
+    runs-on: windows-latest
+    timeout-minutes: 60
+
+    steps:
+      - uses: actions/checkout@v6
+      - name: Setup necessary dotnet SDKs
+        uses: actions/setup-dotnet@v5
+        with:
+          global-json-file: global.json
+          dotnet-version: |
+            10.x
+
+      - name: Install Azure Cosmos DB Emulator
+        shell: pwsh
+        run: ./.github/scripts/windows/install-cosmos-emulator.ps1
+
+      - name: Start Azure Cosmos DB Emulator
+        shell: pwsh
+        run: ./.github/scripts/windows/start-cosmos-emulator.ps1
+
+      - name: Build and test
+        run: ./build.cmd DotnetTest
+        env:
+          CI: true
+          CONFIGURATION: ${{ matrix.configuration }}
+          ENABLE_COVERAGE: false