A memory subsystem can test a memory device in situ, testing the performance of parameters of operation the device in the system it is built into during production. Thus, the system can detect the specific values that will work for one or more operating parameters for the memory device in actual runtime. A test component embedded in the memory subsystem can perform a stress test and identify specific bits or lines of memory that experience failure under one or more stresses. The system can then map out the failed bits or lines to prevent the bits/lines from being used in runtime of the system.