add better metadata handling

tests/test_builder.py

@@ -1,3 +1,4 @@
+import pytest
 from datetime import date
 from zona.models import Metadata
 from zona.builder import split_metadata, discover, build
@@ -24,6 +25,50 @@ description: This is a test.
     assert content == "# Hello World"
 
 
+def test_no_metadata(tmp_path: Path):
+    content = "# Hello World"
+    test_file = tmp_path / "hello-world.md"
+    test_file.write_text(content)
+    meta, content = split_metadata(test_file)
+
+    assert isinstance(meta, Metadata)
+    assert meta.title == "Hello World"
+    assert meta.description is None
+    assert meta.date == date.today()
+    assert content == "# Hello World"
+
+
+def test_malformed_metadata(tmp_path: Path):
+    with pytest.raises(ValueError):
+        tests = {
+            """
+---
+title: Test Post
+date: not a date!!!
+description: This is a test.
+---
+        """,
+            """
+---
+title: Test Post
+foobar:
+    something: what???
+description: This is a test.
+---
+        """,
+            """
+---
+title Test Post
+description: This is a test.
+---
+        """,
+        }
+        for i, content in enumerate(tests):
+            test_file = tmp_path / str(i)
+            test_file.write_text(content)
+            split_metadata(test_file)
+
+
 def test_discover(tmp_path: Path):
     contentd = tmp_path / "content"
     staticd = contentd / "static"