In the Unit Test Window there is a section (called ServerTest) which holds some old tests. I changed that namespace long ago, still this section remains. It holds all tests (which used to be in there) twice. Clicking on the test items has no effect. Running such a test results in a message that that test method cannot be found. Restarting VS does not help.
JustCode 2016.3.914.1 on Win10 Pro 64bit (German)
VS Professional 2015. Version 14.0.25431.01 Update 3
.NET Framework version 4.6.01586