test: add edge case tests for unicode, empty repos, malformed API

Add tests for unicode descriptions, repos with no commits and no
release, malformed JSON responses, HTML responses, control characters
in names, empty and very long descriptions.

fixes #13

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_exporter.py

@@ -93,6 +93,26 @@ class TestSanitizeControlChars:
         assert result[0]["full_name"] == "admin/testrepo"
 
 
+class TestExportJsonEdgeCases:
+    """Test edge cases for JSON export."""
+
+    def test_export_json_empty_description(self):
+        """Empty description produces valid JSON."""
+        repo = _make_repo(description="")
+        output = export_json([repo])
+
+        parsed = json.loads(output)
+        assert parsed[0]["description"] == ""
+
+    def test_export_json_very_long_description(self):
+        """Very long description (10000 chars) produces valid JSON."""
+        repo = _make_repo(description="x" * 10000)
+        output = export_json([repo])
+
+        parsed = json.loads(output)
+        assert len(parsed[0]["description"]) == 10000
+
+
 class TestExportJson:
     """Test export_json function."""