fix value error and add unit test

Author: Ernaldis

datajoint/autopopulate.py

@@ -213,8 +213,7 @@ def handler(signum, frame):
         if not nkeys:
             return
 
-        if processes > 1:
-            processes = min(*(_ for _ in (processes, nkeys, mp.cpu_count()) if _))
+        processes = min(*(_ for _ in (processes, nkeys, mp.cpu_count()) if _))
 
         error_list = []
         populate_kwargs = dict(

tests/test_autopopulate.py

@@ -69,6 +69,15 @@ def test_multi_processing(self):
             == len(self.subject) * self.experiment.fake_experiments_per_subject
         )
 
+    def test_max_multi_processing(self):
+        assert self.subject, "root tables are empty"
+        assert not self.experiment, "table already filled?"
+        self.experiment.populate(processes=None)
+        assert (
+            len(self.experiment)
+            == len(self.subject) * self.experiment.fake_experiments_per_subject
+        )
+
     @raises(DataJointError)
     def test_allow_insert(self):
         assert_true(self.subject, "root tables are empty")