diff --git a/setup.py b/setup.py
index f6c8eff3..3e5356c3 100644
--- a/setup.py
+++ b/setup.py
@@ -9,7 +9,7 @@
 
 cmdclass = {}
 
-install_requires = ['flexx >= 0.4.1',
+install_requires = ['flexx == 0.4.1',
                     'future',
                     'normality == 0.6.1',
                     'dataset == 0.8']
@@ -26,7 +26,7 @@
                                  'tornado == 4.3']
 
 
-version = '0.9.7b0'
+version = '0.9.7b1'
 
 
 setup(name='abcEconomics',
diff --git a/unittest/buy.py b/unittest/buy.py
index e0fdbedd..b079cb7c 100644
--- a/unittest/buy.py
+++ b/unittest/buy.py
@@ -35,10 +35,10 @@ def two(self):
             oo = self.get_offers('cookies')
             assert oo
             for offer in oo:
-                if random.randint(0, 10) == 0:
+                if self.time % 3 == 0:
                     self.tests['not_answered'] = True
                     continue
-                elif random.randint(0, 10) == 0:
+                elif self.time % 3 == 1:
                     self.reject(offer)
                     assert self['money'] == 0
                     assert self['cookies'] == cookies
diff --git a/unittest/give.py b/unittest/give.py
index 63223b56..c811acda 100644
--- a/unittest/give.py
+++ b/unittest/give.py
@@ -21,13 +21,12 @@ def one(self):
 
     def two(self):
         if self.id == 1:
-            rnd = random.randint(0, 1)
-            if rnd == 0:
+            if self.time % 2 == 0:
                 msg = self.get_messages_all()
                 msg = msg['tpc']
                 self.tests['all'] = True
                 assert len(msg) == 1, len(msg)
-            elif rnd == 1:
+            elif self.time % 2 == 1:
                 msg = self.get_messages('tpc')
                 self.tests['topic'] = True
                 assert len(msg) == 1, len(msg)
diff --git a/unittest/sell.py b/unittest/sell.py
index 2caee61a..1b3bf1c6 100644
--- a/unittest/sell.py
+++ b/unittest/sell.py
@@ -1,3 +1,4 @@
+import random
 import abcEconomics
 from tools import is_zero
 import random
@@ -29,17 +30,17 @@ def two(self):
             oo = self.get_offers('cookies')
             assert oo, oo
             for offer in oo:
-                if random.randrange(0, 10) == 0:
+                if self.time % 4 == 0:
                     self.tests['not_answered'] = True
                     continue
-                elif random.randrange(0, 10) == 0:
+                elif self.time % 4 == 1:
                     self.reject(offer)
                     assert self['money'] == money
                     assert self['cookies'] == 0
                     self.tests['rejected'] = True
                     break  # tests the automatic clean-up of polled offers
                 try:
-                    if random.randrange(2) == 0:
+                    if self.time % 4 == 2:
                         self.accept(offer)
                         assert self['cookies'] == offer.quantity
                         assert self['money'] == money - offer.quantity * offer.price
diff --git a/unittest/start_core_engine.py b/unittest/start_core_engine.py
index dd5044a3..1c796593 100644
--- a/unittest/start_core_engine.py
+++ b/unittest/start_core_engine.py
@@ -6,7 +6,7 @@
 
 
 def main(processes, rounds):
-    s = Simulation(processes=processes, name='unittest')
+    s = Simulation(processes=processes, name='unittest', trade_logging='group')
 
     print('build Buy')
     buy = s.build_agents(Buy, 'buy', 1000, rounds=rounds)
@@ -49,7 +49,7 @@ def main(processes, rounds):
 
 
 if __name__ == '__main__':
-    main(processes=1, rounds=3)
+    main(processes=1, rounds=20)
     print('Iteration with 1 core finished')
-    main(processes=2, rounds=3)
+    main(processes=2, rounds=20)
     print('Iteration with multiple processes finished')