Add tests for output.Output and output.File

tests/unit/conftest.py

@@ -0,0 +1,8 @@
+import pytest
+from omicron.ssg.site import Site
+
+
+@pytest.fixture
+def thin_site(tmp_path):
+    (tmp_path / "config.yml").write_text("name: test\ntemplate: plain\n")
+    return Site(tmp_path)