The Unit-Tests do not follow exactly the file structure of Powerlevel9k itself.
Basic Tests belong in test/powerlevel9k.spec if they test basic functionality of
Powerlevel9k itself. Basic functions from the functions directory have their
Tests in separate files under test/functions.
These Tests tend to be more complex in setup than the basic tests. To avoid ending
up in a huge single file, there is one file per segment in test/segments.