[mythhabit]

Just going of the Wikipedia page on unit testing, in the 1956 paper on programming for the SAGE project, refers to testing as: Parameter testing, assembly testing, shake down testing. In the context, parameter testing is testing of individual sub routines (functions/methods). From there the term unit test was used in the Mercury System as unit testing of "individual programs outside and inside the system". I suppose here, the ethos is the same.

Obviously, when reading the rest of the papers, they are clear on the fact, that it is the specifications that the programmer have developed for, that should be tested. That was at the time, synonyms with individual sub routines, and as such it was both the smallest unit and a logical testable unit at the same time. Since then, we've come a long way with programming smaller units with better composability.

I'm not sure I agree that the original meaning of a unit test was lost. Perhaps, only one part of the definition was carried over to modern development practices. In any case, I always stand by the fact that long term value is in tests of the "API". Everything else is implementation details.