I was looking at some code for testing external memory devices recently, which motivated me to try to find some resources on how to properly test memory from software. I found a good article by Michael Barr (an expert author on embedded software topics) which recommends a test strategy and thorough set of tests, along with code examples.
My biggest takeaway from the article was, “… [T]he most common source of actual memory problems is the circuit board. Typical circuit board problems are problems with the wiring between the processor and memory device, missing memory chips, and improperly inserted memory chips.”