test: Ensure empty and None titles are judged invalid

- Check that pages with an empty or `None` title fail validation.
- Use a fixed date in the article test.
- Add a reader-level test using the empty `:title:` source from #3566 to
  confirm readers produce an empty title that is then rejected.

pelican/tests/test_contents.py

@@ -84,8 +84,13 @@ class TestPage(TestBase):
         # If the title is not set, must throw an exception.
         page = Page("content")
         self.assertFalse(page._has_valid_mandatory_properties())
+        # An empty or `None` title must be treated the same as a missing title.
+        for title in ("", None):
+            with self.subTest(title=title):
+                page = Page("content", metadata={"title": title})
+                self.assertFalse(page._has_valid_mandatory_properties())
         self.assertLogCountEqual(
-            count=1,
+            count=3,
             msg="Skipping .*: could not find information about 'title'",
             level=logging.ERROR,
         )
@@ -735,12 +740,10 @@ class TestArticle(TestBase):
         self.assertEqual("custom", custom_article.template)
 
     def test_empty_title_invalid(self):
-        # articles with empty title should be invalid
-        settings = get_settings()
+        # Articles with an empty title should be invalid
         article_kwargs = self._copy_page_kwargs()
         article_kwargs["metadata"]["title"] = ""
-        article_kwargs["metadata"]["date"] = datetime.datetime.now()
-        article_kwargs["settings"] = settings
+        article_kwargs["metadata"]["date"] = datetime.datetime(2026, 2, 9)
         article = Article(**article_kwargs)
         self.assertFalse(article.is_valid())
 

pelican/tests/test_readers.py

@@ -1,7 +1,9 @@
 import os
+from tempfile import TemporaryDirectory
 from unittest.mock import PropertyMock, patch
 
 from pelican import readers
+from pelican.contents import Article
 from pelican.tests.support import get_settings, unittest
 from pelican.utils import SafeDatetime
 
@@ -83,6 +85,25 @@ class DefaultReaderTest(ReaderTest):
         with self.assertRaises(TypeError):
             self.read_file(path="article_with_metadata.unknownextension")
 
+    def test_empty_title_is_invalid(self):
+        """A source file with an empty title must be considered invalid rather
+        than producing a file named ".html"."""
+        sources = {"empty_title.rst": ":title:\n:date: 2026-02-09\n\nContent.\n"}
+        if readers.Markdown:
+            sources["empty_title.md"] = "Title:\nDate: 2026-02-09\n\nContent.\n"
+
+        with TemporaryDirectory() as content_path:
+            r = readers.Readers(settings=get_settings(PATH=content_path))
+            for filename, source in sources.items():
+                with self.subTest(filename=filename):
+                    with open(os.path.join(content_path, filename), "w") as f:
+                        f.write(source)
+                    article = r.read_file(
+                        base_path=content_path, path=filename, content_class=Article
+                    )
+                    self.assertEqual(article.title, "")
+                    self.assertFalse(article.is_valid())
+
     def test_readfile_path_metadata_implicit_dates(self):
         test_file = "article_with_metadata_implicit_dates.html"
         page = self.read_file(path=test_file, DEFAULT_DATE="fs")