This is an example implementation of a testing framework similar to mocha. The point here is just to show what that type of testing framework does and how it could be implemented. This is not intended for real-world use, just for educational purposes.
You can see me live-code this library in this two-part video series:
Note: I made a few changes after the work shown in those videos. Mainly moving the tests into a tests directory, moving the executable into a bin directory, and renaming it.js to tester.js