diff --git a/integration/test_hypothesis_happiness.py b/integration/test_hypothesis_happiness.py
new file mode 100644
index 000000000..83c91ecdd
--- /dev/null
+++ b/integration/test_hypothesis_happiness.py
@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+
+from twisted.trial import unittest
+from hypothesis import given
+from hypothesis.strategies import text, sets
+from allmydata.immutable import happiness_upload
+
+
+class Happiness(unittest.TestCase):
+
+    @given(sets(elements=text(min_size=1), min_size=4, max_size=4), sets(elements=text(min_size=1), min_size=4))
+    def test_hypothesis_unhappy(self, peers, shares):
+        """
+        similar to test_unhappy we test that the resulting happiness is always 4 since the size of peers is 4.
+        """
+        # https://hypothesis.readthedocs.io/en/latest/data.html#hypothesis.strategies.sets
+        # hypothesis.strategies.sets(elements=None, min_size=None, average_size=None, max_size=None)[source]
+        readonly_peers = set()
+        peers_to_shares = {}
+        places = happiness_upload.share_placement(peers, readonly_peers, shares, peers_to_shares)
+        happiness = happiness_upload.calculate_happiness(places)
+        self.assertEqual(4, happiness)
diff --git a/setup.py b/setup.py
index f54a6daf9..86a19e82d 100644
--- a/setup.py
+++ b/setup.py
@@ -284,6 +284,7 @@ setup(name="tahoe-lafs", # also set in __init__.py
               "txi2p >= 0.3.2", # in case pip's resolver doesn't work
               "pytest",
               "pytest-twisted",
+              "hypothesis >= 3.6.1",
           ],
           "tor": [
               "foolscap[tor] >= 0.12.5",
diff --git a/src/allmydata/interfaces.py b/src/allmydata/interfaces.py
index 171f63bcd..7ba5323cd 100644
--- a/src/allmydata/interfaces.py
+++ b/src/allmydata/interfaces.py
@@ -796,7 +796,7 @@ class IPeerSelector(Interface):
         I return whether the share assignments I'm currently using
         reflect a healthy file, based on my internal definitions.
         """
-        
+
     def needs_recomputation():
         """
         I return True if the share assignments I last returned may have
diff --git a/src/allmydata/test/test_happiness.py b/src/allmydata/test/test_happiness.py
index 4fc72ee00..3ebefc3a5 100644
--- a/src/allmydata/test/test_happiness.py
+++ b/src/allmydata/test/test_happiness.py
@@ -31,25 +31,21 @@ class Happiness(unittest.TestCase):
     def test_placement_simple(self):
 
         shares = {'share0', 'share1', 'share2'}
-        peers = {
-            'peer0',
-            'peer1',
-        }
+        peers = {'peer0', 'peer1'}
         readonly_peers = {'peer0'}
         peers_to_shares = {
             'peer0': {'share2'},
             'peer1': [],
         }
 
-        places0 = happiness_upload.share_placement(peers, readonly_peers, shares, peers_to_shares)
+        places = happiness_upload.share_placement(peers, readonly_peers, shares, peers_to_shares)
 
         if False:
-            print("places0")
-            for k, v in places0.items():
+            for k, v in places.items():
                 print("  {} -> {}".format(k, v))
 
         self.assertEqual(
-            places0,
+            places,
             {
                 'share0': {'peer1'},
                 'share1': {'peer1'},
@@ -86,7 +82,7 @@ class Happiness(unittest.TestCase):
             'peerB': set(),
         }
 
-        places0 = happiness_upload.share_placement(peers, readonly_peers, shares, peers_to_shares)
+        places = happiness_upload.share_placement(peers, readonly_peers, shares, peers_to_shares)
 
         # share N maps to peer N
         # i.e. this says that share0 should be on peer0, share1 should
@@ -95,10 +91,9 @@ class Happiness(unittest.TestCase):
             'share{}'.format(i): {'peer{}'.format(i)}
             for i in range(10)
         }
-        self.assertEqual(expected, places0)
+        self.assertEqual(expected, places)
 
     def test_unhappy(self):
-
         shares = {
             'share1', 'share2', 'share3', 'share4', 'share5',
         }
@@ -106,9 +101,7 @@ class Happiness(unittest.TestCase):
             'peer1', 'peer2', 'peer3', 'peer4',
         }
         readonly_peers = set()
-        peers_to_shares = {
-        }
-
+        peers_to_shares = {}
         places = happiness_upload.share_placement(peers, readonly_peers, shares, peers_to_shares)
         happiness = happiness_upload.calculate_happiness(places)
         self.assertEqual(4, happiness)
diff --git a/src/allmydata/util/happinessutil.py b/src/allmydata/util/happinessutil.py
index c5bc03330..3e49dd560 100644
--- a/src/allmydata/util/happinessutil.py
+++ b/src/allmydata/util/happinessutil.py
@@ -4,10 +4,7 @@ reporting it in messages
 """
 
 from copy import deepcopy
-from allmydata.immutable.happiness_upload import share_placement
-from allmydata.immutable.happiness_upload import calculate_happiness
 from allmydata.immutable.happiness_upload import residual_network
-from allmydata.immutable.happiness_upload import bfs
 from allmydata.immutable.happiness_upload import augmenting_path_for