Maintenance testing is:

Maintenance testing refers to the testing that is conducted on a software system that has been changed, either through corrections, enhancements, or other modifications. Its main purpose is to ensure that the changes have been implemented correctly and that the system as a whole continues to function as intended. This type of testing is crucial after a system has been released and needs to be updated or fixed. Maintenance testing ensures that the new changes do not adversely affect the existing functionality of the system​​.REREE33