Source:
http://techfrom10.com/2011/04/the-android-test-market/#

Also see
http://www.pcmag.com/article2/0,2817,2383089,00.asp

From the 2nd referenced article:

<< A possible leak of a test version of the Android Market may have inadvertently confirmed the suspected coming release of Google Music. Although Google has since removed the "Test Market" from the device, others have posted some of the allegdly leaked apps for download. ...>>

http://cdn.androidpolice.netdna-cdn.com/wp-content/uploads/2011/04/snap20110405_061636_thumb.png

And

http://www.blogcdn.com/downloadsquad.switched.com/media/2011/04/music-smaller.jpg