chore: Wire up yeoman unit tests in CI/CD pipelines

build/yaml/templates/component-template.yml

@@ -9,6 +9,7 @@ stages:
         displayName: Build Node project
         steps:
         - template: npm-build-steps.yml
+        - template: npm-test-steps.yml
 
   - stage: stage_package_node
     displayName: 'Node: Build, Version & Pack'
@@ -18,6 +19,7 @@ stages:
         displayName: 'Build & Pack Node project'
         steps:
         - template: npm-build-steps.yml
+        - template: npm-test-steps.yml
         - template: npm-versioning-steps.yml
         - template: npm-package-steps.yml
 

build/yaml/templates/npm-test-steps.yml

@@ -0,0 +1,26 @@
+steps:
+# You are probably wondering "Why not just run 'yarn exec npm run --if-present test'?".
+# On Azure Pipelines, yarn install by default restores modules to a global node_modules cache
+# instead of a local package cache. When running the npm CLI, it is unable to resolve required
+# dependencies as a result, whereas yarn run <script> can do so successfully. However,
+# yarn does not yet have an --if-present condition - the immediate step below simulates this
+# by manually reading the package.json and checking for the presence of $.scripts.test in the JSON.
+- powershell: |
+    if (Test-Path -Path package.json) {
+      $package = Get-Content package.json | ConvertFrom-Json
+      $result = $package.scripts -and $package.scripts.test
+      Write-Host "##vso[task.setvariable variable=NpmRunTest;]$result"
+    } else {
+      Write-Host "Missing package.json"
+      exit 1
+    }
+  displayName: 'Determine if test script is present'
+  name: SetNpmRunTest
+  workingDirectory: '$(WorkingDirectory)'
+
+- script: |
+    yarn run test
+  condition: eq(variables.NpmRunTest, true)
+  continueOnError: true
+  displayName: 'Run test if it exists'
+  workingDirectory: '$(WorkingDirectory)'