We lost FTL tests at some point, possibly during L20n to FTL migration. We should add them.
This bug is about adding test coverage for the FTL format support in our sync application.
A simple way to look at it is to open this folder: https://github.com/mozilla/pontoon/tree/master/pontoon/sync/tests/formats
We basically want to add a test_ftl.py file there, and write a series of tests to make sure we support the FTL format correctly. The code to test is in this file: https://github.com/mozilla/pontoon/blob/master/pontoon/sync/formats/ftl.py
I suggest taking a look at both the code and what other format tests are doing, and use that as inspiration. Tests should be testing regular code paths, and also edge cases if there are any.