diff --git a/.github/workflows/build-test-deploy.yml b/.github/workflows/build-test-deploy.yml
index 47a0af7..7c5744d 100644
--- a/.github/workflows/build-test-deploy.yml
+++ b/.github/workflows/build-test-deploy.yml
@@ -64,11 +64,36 @@ jobs:
           path: build/ # the Jekyll build directory
           include-hidden-files: true # Workaround https://github.com/actions/upload-artifact/issues/610
 
+  # Test the test tools themselves
+  test-test:
+    name: Test tools validation
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      # Installing Node + modern Yarn on GitHub Actions requires hack
+      # https://github.com/actions/setup-node/issues/531#issuecomment-2960522861
+      - name: Install Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version-file: .nvmrc
+      - name: Enable Corepack
+        run: corepack enable
+      - name: Configure dependency cache
+        uses: actions/setup-node@v4
+        with:
+          cache: yarn
+      - name: Install dependencies
+        run: yarn install --immutable
+
+      - name: Test test tools
+        run: yarn run test-test
+
   # Test the build artifact
   test:
     name: Test
     runs-on: ubuntu-latest
-    needs: build
+    needs: [build, test-test]
     steps:
       - uses: actions/checkout@v4
 
diff --git a/package.json b/package.json
index b536272..1a76422 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,8 @@
     "structured-data-testing-tool": "^4.5.0"
   },
   "scripts": {
-    "test": "yarn node test/fixtures-html-validate-should-fail.mjs && yarn node test/fixtures-structured-data-should-fail.mjs && yarn node test/build-html-validate.mjs && yarn node test/dirty-file-paths-checker.mjs && yarn node test/build-structured-data-validate.mjs",
+    "test": "yarn node test/build-html-validate.mjs && yarn node test/dirty-file-paths-checker.mjs && yarn node test/build-structured-data-validate.mjs",
+    "test-test": "yarn node test/fixtures-html-validate-should-fail.mjs && yarn node test/fixtures-structured-data-should-fail.mjs",
     "test-structured-data": "yarn node test/build-structured-data-validate.mjs",
     "lint": "yarn prettier-check && yarn markdownlint-check",
     "lint-fix": "yarn prettier-fix && yarn markdownlint-fix",