My point earlier was that under the "Given, When, Then" structure, these locales are part of the given information.

The current structure is: When we parse this file, then it has this source locale and it has these translation locales.

The structure I suggest is: Given that this file has a tmx with these locales and this source language, when we parse it, then the source language matches the one from the file and the translation locales match those in the file.