Recently, while interviewing a person, I came up with an interesting question. That led to a series of discoveries about the interviewee. So I thought I would share it here.

How does xUnit work? **

This one question offered insight into various aspects that I cared about. I steered the discussion until I got the answers to these question, without asking them explicitly.

• Do you know what unit testing is? - Awareness level
• When do you write test cases? Before or after the change? - Practitioner skills
• How does unit testing work? - Conceptual skills
• Do you understand annotations? How are they used in JUnit / NUnit? - Advanced developer skills
• Do you understand the implementation behind unit test frameworks, or are you a dumb consumer? - Architectural skills
• How was the implementation explained? - Communication skills

What are your favourite questions?

** Replace xUnit with language specific implementation (JUnit, NUnit, etc.).