> If you find your testers splitting up functions to support the testing process, you’re destroying your system architecture and code comprehension along with it. Test at a coarser level of granularity.

The emphasis here should be on the reason for splitting up functions. Long, complex functions can be difficult to understand, and removing a few lines in exchange for a (well named) function call is very beneficial for the reader. The opportunity for testing comes from this delegation. A function call is a contract, and the test ensures it complies. Now the reader can comprehend what the code is doing at a higher level; trusting the sub functions do what they intend.