The Testing Maturity Model (TMM) was based on the Capability Maturity Model, and first produced by the Illinois Institute of Technology.
Its aim to be used in a similar way to CMM, that is to provide a framework for assessing the maturity of the test processes in an organisation, and so providing targets on improving maturity.
Each level from 2 upwards has a defined set of processes and goals, which lead to practices and sub-practices.
The TMM has been since replaced by the Test Maturity Model integration and is now managed by the TMMI Foundation.
References
Testing Maturity Model Wikipedia(Text) CC BY-SA