The test above (`AcceptCallsVisitOnceWithCorrectType`) in this (old) commit uses a Strict Mock, because the `SequenceEqual` method will only return `true` if it *only* observed `sut`.

The previous version of `AcceptReturnsTheCorrectVisitorInstance` didn't do *Data Flow Verification* because it never checked the input. In other words, it resembled the use of `It.IsAny<T>()`.

The new test in 18ddc9c8de207784767f44eca2f25b6f93398aa9 correctly does *Data Flow Verification*.

HTH