What is xUnit Fact versus Theory?
PICTURE THIS: DATA SPLIT
Fit on train, tune on val, report on test once.
Simple meaning
Fact is a single test.
WHY — Testing instead of guessing?
Why interviewers care about Testing:
contrast on Testing, not two memorised paragraphs.
the developer, then one case where picking wrong hurts.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Define it
Fact is a single test.
- 2Theory runs the same
test with InlineData rows.
- 3Theories catch edge cases
without copy-paste.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Fact is a single test. Theory runs the same test with InlineData rows.