test: increase coverage slightly

metacov.ini

@@ -73,6 +73,9 @@ exclude_lines =
     # longer tested.
     pragma: obscure
 
+    # Lines that will never be called, but satisfy the type checker
+    pragma: never called
+
 partial_branches =
     pragma: part covered
     # A for-loop that always hits its break statement

tests/test_plugins.py

@@ -33,7 +33,7 @@
 class NullConfig(TPluginConfig):
     """A plugin configure thing when we don't really need one."""
     def get_plugin_options(self, plugin: str) -> TConfigSectionOut:
-        return {}
+        return {}   # pragma: never called
 
 
 class FakeConfig(TPluginConfig):
@@ -284,7 +284,8 @@ def test_exception_if_plugins_on_pytracer(self) -> None:
 
         if testenv.PY_TRACER:
             core = "PyTracer"
-        elif testenv.SYS_MON:
+        else:
+            assert testenv.SYS_MON
             core = "SysMonitor"
 
         expected_warnings = [