How do you test private/internal members in .NET?

Short answer: Test private members indirectly through public methods. For internal members, use the [InternalsVisibleTo] attribute to expose them to test assemblies.

Real-world example (ShopNest)

ShopNest unit tests cover pricing and discount rules so a bad coupon change fails in CI before customers see it.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.