Property-test Markdown frontmatter parsing

docs/lessons-learned.md

@@ -69,6 +69,7 @@ This document records project lessons that should guide future changes to Python
 - Unit tests are good for catalog integrity, rendering contracts, Dynamic Worker code generation, and cache-policy source checks.
 - Browser tests are necessary for Shiki/CodeMirror layout behavior and visual regressions.
 - Local `uv run ...` can hide CI import assumptions. GitHub's verify job may invoke `python3 -m unittest` before runtime dependencies such as FastAPI are importable, so tests that import `src/main.py` should either install the dependency explicitly or stub FastAPI/Starlette/Workers modules with purpose-built fakes.
+- Example source files cross a TOML/Markdown grammar boundary. Generate valid TOML fields and an independent arbitrary Markdown body, then assert exact metadata, exact body preservation, and the first body line through `_split_frontmatter`. Arbitrary text alone rarely reaches the valid-frontmatter path, while properties that rebuild the parser's result can repeat its bug.
 - SEO and cache-busting deserve a dedicated linter because errors are easy to reintroduce when adding pages or assets.
 - Always run the full pre-push set before publishing. Start `pywrangler dev --port 9696`, then run:
 

package.json

@@ -10,6 +10,6 @@
     "node": "22.x"
   },
   "devDependencies": {
-    "wrangler": "4.114.0"
+    "wrangler": "4.127.1"
   }
 }

pyproject.toml

@@ -14,6 +14,7 @@ workers = [
     "workers-runtime-sdk",
 ]
 dev = [
+    "hypothesis>=6.0",
     "pillow>=11.3,<12",
     "ruff==0.16.0",
 ]

tests/test_app.py

@@ -447,9 +447,9 @@ def test_generated_drift_is_blocked_before_commit_and_merge(self):
         self.assertIn('"preview_urls": false', wrangler_config)
         package = json.loads((ROOT / "package.json").read_text())
         lock = json.loads((ROOT / "package-lock.json").read_text())
-        self.assertEqual(package["devDependencies"]["wrangler"], "4.114.0")
+        self.assertEqual(package["devDependencies"]["wrangler"], "4.127.1")
         self.assertEqual(package["engines"]["node"], "22.x")
-        self.assertEqual(lock["packages"][""]["devDependencies"]["wrangler"], "4.114.0")
+        self.assertEqual(lock["packages"][""]["devDependencies"]["wrangler"], "4.127.1")
         makefile = (ROOT / "Makefile").read_text()
         self.assertIn("check-node-version", makefile)
         self.assertIn("pywrangler sync --force", makefile)

tests/test_parser_properties.py

@@ -0,0 +1,45 @@
+"""Structured properties for the Markdown example source boundary."""
+
+import json
+import unittest
+
+from hypothesis import given
+from hypothesis import strategies as st
+from src.example_loader import _split_frontmatter
+
+TOML_TEXT = st.text(
+    alphabet=st.characters(blacklist_categories=("Cc", "Cs")),
+    max_size=200,
+)
+MARKDOWN_BODY = st.text(max_size=1_000)
+
+
+class ExampleSourceParserProperties(unittest.TestCase):
+    @given(slug=TOML_TEXT, title=TOML_TEXT, body=MARKDOWN_BODY)
+    def test_toml_frontmatter_round_trips_without_changing_markdown(
+        self,
+        slug,
+        title,
+        body,
+    ):
+        """Generated TOML metadata and arbitrary Markdown stay separated."""
+        source = (
+            "+++\n"
+            f"slug = {json.dumps(slug, ensure_ascii=False)}\n"
+            f"title = {json.dumps(title, ensure_ascii=False)}\n"
+            "+++\n"
+            f"{body}"
+        )
+
+        metadata, parsed_body, body_line = _split_frontmatter(
+            source,
+            "generated.md",
+        )
+
+        self.assertEqual(metadata, {"slug": slug, "title": title})
+        self.assertEqual(parsed_body, body)
+        self.assertEqual(body_line, 5)
+
+
+if __name__ == "__main__":
+    unittest.main()