You need the final implementation before taking the final snapshot but you can write the entire test up front (given/when). The snapshot artefact is generated not written (often in a different file entirely), so Id argue it still fits the definition cleanly.

I agree that "unit test"/"integration test" as a definition sucks horribly and leads to people talking past each other, but I think with TDD the main issue is that lots of people have developed a fixed and narrow idea of the kind of test you are "supposed" to write with it which makes the process miserable if the type of code doesnt fit that type of test.

The whole idea of a unit test being "the" kind of "default" test and being "tests a class/method as a unit" definitely needs to die.