OTHER: Add mutation testing with Stryker

.github/workflows/pull_request.yml

@@ -13,3 +13,44 @@ jobs:
     test:
         name: Test
         uses: recrafter-group/.github/.github/workflows/test.yml@version/2.0.0
+    mutation_test:
+        name: Mutation test
+        runs-on: ubuntu-22.04
+        permissions:
+            contents: read
+            pull-requests: write
+        steps:
+            - name: Check out Git repository
+              uses: actions/checkout@v4.2.2
+            - name: Set up Node.js
+              uses: actions/setup-node@v4.4.0
+              with:
+                  node-version: 22
+                  cache: npm
+            - name: Install Node.js dependencies
+              run: npm ci
+            - name: Run mutation tests
+              run: npm run test:mutation
+            - name: Upload mutation report
+              id: upload-mutation-report
+              if: ${{ !cancelled() }}
+              uses: actions/upload-artifact@v4.4.3
+              with:
+                  name: mutation-report
+                  path: ./.stryker/reports/
+                  if-no-files-found: error
+                  include-hidden-files: true
+            - name: Build mutation report comment
+              if: ${{ !cancelled() }}
+              run: |
+                  echo '## Mutation testing' > mutation-comment.md
+                  echo '' >> mutation-comment.md
+                  cat .stryker/reports/mutation.md >> mutation-comment.md
+                  echo '' >> mutation-comment.md
+                  echo "[Download report](${{ steps.upload-mutation-report.outputs.artifact-url }})" >> mutation-comment.md
+            - name: Comment mutation report on pull request
+              if: ${{ !cancelled() }}
+              uses: marocchino/sticky-pull-request-comment@v3.0.2
+              with:
+                  header: mutation
+                  path: mutation-comment.md

.gitignore

@@ -1,4 +1,5 @@
 node_modules/
 .package/
 .coverage/
+.stryker/
 *.log