diff --git a/chainsyncer/driver.py b/chainsyncer/driver.py
index 440e9ae..e652a3b 100644
--- a/chainsyncer/driver.py
+++ b/chainsyncer/driver.py
@@ -72,8 +72,8 @@ class Syncer:
         self.backend.register_filter(str(f))
 
 
-    def process_single(self, conn, block, tx, block_height, tx_index):
-        self.backend.set(block_height, tx_index)
+    def process_single(self, conn, block, tx):
+        self.backend.set(block.number, tx.index)
         self.filter.apply(conn, block, tx)
 
 
@@ -133,7 +133,7 @@ class HeadSyncer(BlockPollSyncer):
             rcpt = conn.do(receipt(tx.hash))
             tx.apply_receipt(rcpt)
     
-            self.process_single(conn, block, tx, block.number, i)
+            self.process_single(conn, block, tx)
                         
             i += 1
         
diff --git a/chainsyncer/unittest/base.py b/chainsyncer/unittest/base.py
new file mode 100644
index 0000000..9e320e5
--- /dev/null
+++ b/chainsyncer/unittest/base.py
@@ -0,0 +1,59 @@
+# standard imports
+import os
+
+# external imports
+from hexathon import add_0x
+
+# local imports
+from chainsyncer.driver import HistorySyncer
+from chainsyncer.error import NoBlockForYou
+
+
+class MockTx:
+
+    def __init__(self, tx_hash, index):
+        self.hash = tx_hash
+        self.index = index
+
+
+class MockBlock:
+
+    def __init__(self, number, txs):
+        self.number = number
+        self.txs = txs
+
+
+    def tx(self, i):
+        return MockTx(i, self.txs[i])
+
+
+class TestSyncer(HistorySyncer):
+
+
+    def __init__(self, backend, tx_counts=[]):
+        self.tx_counts = tx_counts
+        super(TestSyncer, self).__init__(backend)
+
+
+    def get(self, conn):
+        if self.backend.block_height == self.backend.target_block:
+            self.running = False
+            raise NoBlockForYou()
+        if self.backend.block_height > len(self.tx_counts):
+            return []
+
+        block_txs = []
+        for i in range(self.tx_counts[self.backend.block_height]):
+            block_txs.append(add_0x(os.urandom(32).hex()))
+      
+        return MockBlock(self.backend.block_height, block_txs)
+
+
+    def process(self, conn, block):
+        i = 0
+        for tx in block.txs:
+            self.process_single(conn, block, tx)
+            i += 1
+        self.backend.set(self.backend.block_height + 1, 0)
+
+
diff --git a/tests/test_interrupt.py b/tests/test_interrupt.py
index 4cd61c4..9f4203d 100644
--- a/tests/test_interrupt.py
+++ b/tests/test_interrupt.py
@@ -9,45 +9,18 @@ from hexathon import add_0x
 
 # local imports
 from chainsyncer.backend.memory import MemBackend
-from chainsyncer.driver import HeadSyncer
-from chainsyncer.error import NoBlockForYou
 
 # test imports
 from tests.base import TestBase
+from chainsyncer.unittest.base import (
+        MockBlock,
+        TestSyncer,
+        )
 
 logging.basicConfig(level=logging.DEBUG)
 logg = logging.getLogger()
 
 
-class TestSyncer(HeadSyncer):
-
-
-    def __init__(self, backend, tx_counts=[]):
-        self.tx_counts = tx_counts
-        super(TestSyncer, self).__init__(backend)
-
-
-    def get(self, conn):
-        if self.backend.block_height == self.backend.target_block:
-            raise NoBlockForYou()
-        if self.backend.block_height > len(self.tx_counts):
-            return []
-
-        block_txs = []
-        for i in range(self.tx_counts[self.backend.block_height]):
-            block_txs.append(add_0x(os.urandom(32).hex()))
-      
-        return block_txs
-
-
-    def process(self, conn, block):
-        i = 0
-        for tx in block:
-            self.process_single(conn, block, tx, self.backend.block_height, i)
-            i += 1
-
-
-
 class NaughtyCountExceptionFilter:
 
     def __init__(self, name, croak_on):
@@ -100,7 +73,16 @@ class TestInterrupt(unittest.TestCase):
         for fltr in fltrs:
             self.syncer.add_filter(fltr)
 
+        try:
+            self.syncer.loop(0.1, None)
+        except RuntimeError:
+            pass
         self.syncer.loop(0.1, None)
 
+        for fltr in fltrs:
+            logg.debug('{} {}'.format(str(fltr), fltr.c))
+            self.assertEqual(fltr.c, 9)
+
+
 if __name__ == '__main__':
     unittest.main()