How do you test a romance scammer?

How do you typically go about testing someone you suspect of being a romance scammer? Do you have a specific set of questions or techniques that you use to uncover their true intentions? What signs or behaviors do you look for that might indicate they're trying to deceive you for financial gain? Is there a particular approach that has proven to be most effective in your experience? And how do you handle the situation if you do uncover that they're a scammer?