runtests works in matlab 2015b but not in 2013b

I tryed the runtests function example at http://ift.tt/1EKhs3e and in matlab 2015b everthing works perfectly. But in matlab 2013b I get the following error

>> runtests
Error using runtests (line 41)
Not enough input arguments.

And if I explizietly one of the m-files

>> runtests('typeTest.m')

I get

Error using matlab.unittest.TestSuite.fromFile (line 94)
"C:\Users\u16h62\Documents\MATLAB\Example\typeTest.m" is not a valid test    file.
 Error in runtests>createSuite (line 60)
 suite = TestSuite.fromFile(file);
 Error in runtests>@(test)createSuite(test,parser.Results.Recursively) (line   41)
suites = cellfun(@(test)createSuite(test, parser.Results.Recursively), ...
Error in runtests (line 41)
suites = cellfun(@(test)createSuite(test, parser.Results.Recursively), ...

Can someone say me what I am doing wrong, please?