Introduce MethodMissingObjectTest
Introduce MethodMissingObjectTest

Previously this class had no unit test coverage.

I'm planning to make changes to `MethodMissingObject`, so it makes sense to add
some coverage before starting to make the changes.

aledelcueto/smart-answers,alphagov/smart-answers,alphagov/smart-answers,aledelcueto/smart-answers,alphagov/smart-answers,stwalsh/smart-answers,aledelcueto/smart-answers,stwalsh/smart-answers,stwalsh/smart-answers,alphagov/smart-answers,aledelcueto/smart-answers,stwalsh/smart-answers