Tone deafness is a real condition (it's a subset of the more general condition "amusia") but is often confused with learned musical abilities, particularly being able to sing in tune. True tone deafness is something (which most studies agree) only 1-3% of the general population suffer from.
If you are truly tone deaf you will be unable to really enjoy or appreciate music. For that reason many people take these tests and declare them "too easy" but if the test is well designed it should be easy for 99% of people. This is an example of people misusing the phrase "tone deaf" to mean "not skilled in music".
If anybody would like to try some other tests for tone deafness (some good, some terrible, and disclaimer: one made by me) I wrote up a summary of the most popular ones online here: http://www.easyeartraining.com/learn/tone-deaf-tests-online/