I am just thinking - ISO 9001 of course say you need to have some quality control and quality assurance activities but it is up to you to define it and document it.
CMMI is not mandatory (it does tell you to do validation and verification to achieve Level 3).
But are there any norms/standards that actually prescribe to perform testing on software? I believe this might be just the SIL for low level SW controlling hardware in cars etc..But to be honest, I do not know if ISO 61508, defining SIL, actually dictates the testing must be done - for SIL levels, it is under "recommended" or "highly recommended".
EDIT: The title edit was not correct, there are many standards for software testing itself.