[Product-Developers] Running tests from a Plone 3 buildout

[Hedley Roos]

I'm having trouble running tests for Archetypes 1.5.8.

I stand in directory /path/to/my_instance/parts/instance/bin and do 
./zopectl test -s Products.Archetypes

I just get

Running tests at level 1
Total: 0 tests, 0 failures, 0 errors

I've tried a few permutations but no success. What am I doing wrong? I 
do have ZopeTestCase and PloneTestCase in my products directory.

Hedley