NF: test can pick up extension test suites and run them too

Without requiring a user to keep track of what extensions are installed
on a particular system.

datalad/interface/test.py

@@ -15,6 +15,7 @@
 import datalad
 from .base import Interface
 from datalad.interface.base import build_doc
+from datalad.utils import assure_list
 from ..support.param import Parameter
 
 
@@ -23,7 +24,7 @@ class Test(Interface):
     """Run internal DataLad (unit)tests.
 
     This can be used to verify correct operation on the system.
-    It is just a thin wrapper around a call to nose, so number of 
+    It is just a thin wrapper around a call to nose, so number of
     exposed options is minimal
     """
     # XXX prevent common args from being added to the docstring
@@ -48,10 +49,17 @@ class Test(Interface):
             doc="stop running tests after the first error or failure"),
         module=Parameter(
             args=("module",),
-            nargs="?",
-            doc="be verbose - list test names"),
+            nargs="*",
+            doc="""test name(s), by default all tests of DataLad core and any
+            installed extensions are executed"""),
     )
 
     @staticmethod
-    def __call__(module='datalad', verbose=False, nocapture=False, pdb=False, stop=False):
-        datalad.test(module=module, verbose=verbose, nocapture=nocapture, pdb=pdb, stop=stop)
+    def __call__(module=None, verbose=False, nocapture=False, pdb=False, stop=False):
+        if module is None:
+            from pkg_resources import iter_entry_points
+            module = ['datalad']
+            module.extend(ep.module_name for ep in iter_entry_points('datalad.tests'))
+        module = assure_list(module)
+        for mod in module:
+            datalad.test(module=mod, verbose=verbose, nocapture=nocapture, pdb=pdb, stop=stop)