Add delimiter between global stuff and test cases

Helps provide some oversight since this module is about to explode in size.

Contributes to issue CURA-3497.

tests/Settings/TestExtruderStack.py

@@ -12,6 +12,8 @@ from cura.Settings.Exceptions import InvalidOperationError #To check whether the
 def extruder_stack() -> cura.Settings.ExtruderStack.ExtruderStack:
     return cura.Settings.ExtruderStack.ExtruderStack
 
+#############################START OF TEST CASES################################
+
 ##  Tests whether adding a container is properly forbidden.
 def test_addContainer(extruder_stack):
     with pytest.raises(InvalidOperationError):