Where are the Arduino Function Unit Tests kept? I want to submit a fix for a faulty Arduino function

Question

I have coded a fix for a major problem with the Arduino map function (in Arduino.h & arduino/avr/cores/arduino/WMath.cpp).

I submitted it as a comment to map function causes huge errors when mapping to small intervals due to integer truncation #10382 but heard nothing so far.

I thought it might be handled quicker if I can submit it as a Pull Request with Unit Tests to A) expose how and why map is faulty and B) show how my solution fixes the problem.