A memory subsystem includes a test signal generator of a memory controller that generates a test data signal in response to the memory controller receiving a test transaction. The test transaction indicates one or more I/O operations to perform on an associated memory device. The test signal generator can generate data signals from various different pattern generators. The memory controller scheduler schedules the test data signal pattern, and sends it to the memory device. The memory device can then execute I/O operation(s) to implement the test transaction. The memory controller can read back data written to a specific address of the memory device and compare the read back data with expected data. When the read back data and the expected data do not match, the memory controller can record an error. The error can include the specific address of the error, the specific data, and/or encoded data.