add mock_return; to tack's test
add mock_return; to tack's test

RobertoMalatesta/glshim,seandepagnier/glshim,RobertoMalatesta/glshim,RobertoMalatesta/glshim,RobertoMalatesta/glshim,lunixbochs/glshim,lunixbochs/glshim,seandepagnier/glshim,lunixbochs/glshim,lunixbochs/glshim,seandepagnier/glshim,seandepagnier/glshim