How do you verify that a method was called on a mock object?

Short answer: mockService.Verify(s => s.Save(), Times.Once); This asserts that Save() was called exactly once during the test.

Example code

mockService.Verify(s => s.Save(), Times.Once); This asserts that Save() was called exactly once during the test.

Real-world example (ShopNest)

When testing ShopNest’s order service, mock IPaymentGateway so tests do not call Razorpay.

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.