Maxim Tester
Take Kant's own examples step by step through the test of the categorical imperative.
The subjective principle of action — the personal rule on which someone actually acts.
Every action, for Kant, follows a maxim whether we articulate it or not (“when short of money, I borrow and promise to repay …”). What is morally tested is not the single deed but this underlying rule: the categorical imperative asks whether the maxim can be conceived and willed as a universal law.
Source: Wikipedia: Maxim