Revising the diagnosis of congenital amusia with the Montreal Battery of Evaluation of Amusia
This 2015 article presents: "a critical survey of the prevalent usage of the Montreal Battery of Evaluation of Amusia (MBEA; Peretz et al., 2003) to assess congenital amusia, a neuro-developmental disorder that has been claimed to be present in 4% of the population (Kalmus and Fry, 1980)." Read the full text here here.
One of the conclusions is that online tests for amusia are not as reliable as one would hope. Testing in a laboratory environment is preferable. I have put "find a list of labs that offer amusia tests" on my list of things to be done.