This is a project by Building SMART to generate example IFC files. Primarily for IFC4 (but not restricted to this schema), it is intended to concentrate on samples and unit tests demonstrating features and improvements implemented for this schema.
You can find an introduction and explanation of the project here https://www.youtube.com/watch?v=0g3rTPQKONE&list=UU01FBzTNN-umc7w1-MYnABw
It uses the Geometry Gym library for generating the classes and files, essentially as a series of constructors. You can contact Jon for details about how to license this assembly.
If you have suggestions or requests for further examples, or wish to contribute, then please don't hesitate to get in contact.