sure! write a few tests pretending your thing is already implemented, to capture what you want it to do. at this point it's a step beyond writing no test and just typing `YourThing.Do()` in a text editor. does it make sense? is it awkward? should it even be `YourThing` or `SomeOtherThing`? what the "unit" is of what you're testing might change, or its API might. you're basically just trying to get a sketch of what it's like for the user.

now, at the end of this, you'll have a clearer idea of the external API boundary, probably a clearer vision of how it should work, _and_ code you can test against. you've potentially just saved yourself the labour of writing the thing, realizing it needs to be redesigned, and rewriting it.