The GCDSpec test class comment document:
/**
* This is a trivial example of how to run this Specification
* From within sbt use:
* {{{
* testOnly gcd.GcdDecoupledTester
* }}}
* From a terminal shell use:
* {{{
* sbt 'testOnly gcd.GcdDecoupledTester'
* }}}
*/
the class GCDSpec
should be named GcdDecoupledTester
or change the comment
testOnly gcd.GcdDecoupledTester
to testOnly gcd.GCDSpec