ok, tried with a new project and it seems to work fine using the same config .. I ended up removing all the tests (inc the tests folder) from the project and it seemed to start working there were a couple of failing tests but that looked ok otherwise -- not sure what is going on with that.

@pdmct That's good to know. I wonder if you had some top-level code, outside tests etc, that was causing problems being executed when the tests were loaded?

Perhaps left over from an earlier experiment and not deleted or placed into a deftest...

@seancorfield not sure, I haven't put them back in yet but there was something funky going on with them. I might re-introduce them gradually and see if I can find what is going wrong. Thanks for your help.