diff --git a/src/tests/test_proofofwork.py b/src/tests/test_proofofwork.py
index 2356ed73..d3c1d6fd 100644
--- a/src/tests/test_proofofwork.py
+++ b/src/tests/test_proofofwork.py
@@ -10,9 +10,14 @@ import unittest
 from struct import pack, unpack
 
 from pybitmessage import proofofwork, protocol
+from pybitmessage.defaults import (
+    networkDefaultProofOfWorkNonceTrialsPerByte,
+    networkDefaultPayloadLengthExtraBytes)
 
 from .samples import sample_pow_target, sample_pow_initial_hash
 
+default_ttl = 7200
+
 
 class TestProofofworkBase(unittest.TestCase):
     """Basic test case for proofofwork"""
@@ -22,13 +27,13 @@ class TestProofofworkBase(unittest.TestCase):
         proofofwork.init()
 
     @staticmethod
-    def _make_sample_payload(TTL=7200):
+    def _make_sample_payload(TTL=default_ttl):
         return pack('>Q', int(time.time() + TTL)) + os.urandom(166)
 
     def test_calculate(self):
         """Ensure a calculated nonce has sufficient work for the protocol"""
         payload = self._make_sample_payload()
-        nonce = proofofwork.calculate(payload, 7200)[1]
+        nonce = proofofwork.calculate(payload, default_ttl)[1]
         self.assertTrue(
             protocol.isProofOfWorkSufficient(pack('>Q', nonce) + payload))
 
@@ -38,6 +43,22 @@ class TestProofofworkBase(unittest.TestCase):
 class TestProofofwork(TestProofofworkBase):
     """The main test case for proofofwork"""
 
+    @classmethod
+    def tearDownClass(cls):
+        import state
+        state.shutdown = 0
+
+    def setUp(self):
+        self.tearDownClass()
+
+    def _make_sample_data(self):
+        payload = self._make_sample_payload()
+        return payload, proofofwork.getTarget(
+            len(payload), default_ttl,
+            networkDefaultProofOfWorkNonceTrialsPerByte,
+            networkDefaultPayloadLengthExtraBytes
+        ), hashlib.sha512(payload).digest()
+
     def test_calculate(self):
         """Extended test for the main proofofwork call"""
         # raise difficulty and TTL
@@ -49,7 +70,13 @@ class TestProofofwork(TestProofofworkBase):
                 pack('>Q', nonce) + payload, 2000, 2000,
                 int(time.time()) + TTL - 3600))
 
-    def test_with_target(self):
+        import state
+
+        with self.assertRaises(StopIteration):
+            state.shutdown = 1
+            proofofwork.calculate(payload, TTL)
+
+    def test_CPoW(self):
         """Do PoW with parameters from test_openclpow and check the result"""
         nonce = proofofwork._doCPoW(
             sample_pow_target, sample_pow_initial_hash)[0]
@@ -58,3 +85,17 @@ class TestProofofwork(TestProofofworkBase):
                 pack('>Q', nonce) + sample_pow_initial_hash
             ).digest()).digest()[0:8])
         self.assertLess((nonce - trial_value), sample_pow_target)
+
+    def test_SafePoW(self):
+        """Do python PoW for a sample payload and check by protocol"""
+        payload, target, initial_hash = self._make_sample_data()
+        nonce = proofofwork._doSafePoW(target, initial_hash)[1]
+        self.assertTrue(
+            protocol.isProofOfWorkSufficient(pack('>Q', nonce) + payload))
+
+    def test_FastPoW(self):
+        """Do python multiprocessing PoW for a sample payload and check"""
+        payload, target, initial_hash = self._make_sample_data()
+        nonce = proofofwork._doFastPoW(target, initial_hash)[1]
+        self.assertTrue(
+            protocol.isProofOfWorkSufficient(pack('>Q', nonce) + payload))