As I said, an interface can easily be tested, but if it’s internal implementation I normally make a design, implement it, and I usually come up with other ideas and I like having the fluidity of making changes as I prototype and such, that way I’m not constrained by a test yet. After I’m done, and documented my choices if necessary, then I add the tests.
I mean I’m theory for any planned method you would know the input and expected output before the coffee is written.
As I said, an interface can easily be tested, but if it’s internal implementation I normally make a design, implement it, and I usually come up with other ideas and I like having the fluidity of making changes as I prototype and such, that way I’m not constrained by a test yet. After I’m done, and documented my choices if necessary, then I add the tests.