diff --git a/chainsyncer/unittest/base.py b/chainsyncer/unittest/base.py
index a02a388..f33a43b 100644
--- a/chainsyncer/unittest/base.py
+++ b/chainsyncer/unittest/base.py
@@ -28,6 +28,27 @@ class MockFilterError(Exception):
     pass
 
 
+class MockBlockGenerator:
+
+    def __init__(self, offset=0):
+        self.blocks = {}
+        self.offset = offset
+        self.cursor = offset
+
+
+    def generate(self, spec=[], driver=None):
+        for v in spec:
+            txs = []
+            for i in range(v):
+                tx_hash = os.urandom(32).hex()
+                tx = MockTx(0, tx_hash)
+                txs.append(tx)
+
+            block = MockBlock(self.cursor, txs)
+            driver.add_block(block)
+            self.cursor += 1
+
+
 class MockConn:
     """Noop connection mocker.
 
@@ -72,6 +93,7 @@ class MockBlock:
         """
         self.number = number
         self.txs = txs
+        self.hash = os.urandom(32).hex()
 
 
     def tx(self, i):
@@ -141,6 +163,7 @@ class MockDriver(SyncDriver):
 
 
     def add_block(self, block):
+        logg.debug('add block {} {} with {} txs'.format(block.number, block.hash, len(block.txs)))
         self.blocks[block.number] = block
 
 
diff --git a/tests/test_session.py b/tests/test_session.py
index 9d58f9a..7823e36 100644
--- a/tests/test_session.py
+++ b/tests/test_session.py
@@ -16,6 +16,7 @@ from chainsyncer.error import (
         SyncDone,
         )
 from chainsyncer.unittest import (
+        MockBlockGenerator,
         MockFilter,
         MockConn,
         MockTx,
@@ -63,18 +64,8 @@ class TestFilter(unittest.TestCase):
 
     def test_driver(self):
         drv = MockDriver(self.store, target=1)
-
-        tx_hash = os.urandom(32).hex()
-        tx = MockTx(0, tx_hash)
-        block = MockBlock(0, [tx_hash])
-        drv.add_block(block)
-
-        tx_hash_one = os.urandom(32).hex()
-        tx = MockTx(0, tx_hash_one)
-        tx_hash_two = os.urandom(32).hex()
-        tx = MockTx(1, tx_hash_two)
-        block = MockBlock(1, [tx_hash_one, tx_hash_two])
-        drv.add_block(block)
+        generator = MockBlockGenerator()
+        generator.generate([1, 2], driver=drv)
 
         fltr_one = MockFilter('foo')
         self.store.register(fltr_one)
@@ -86,11 +77,8 @@ class TestFilter(unittest.TestCase):
 
     def test_driver_interrupt_noresume(self):
         drv = MockDriver(self.store, target=1)
-
-        tx_hash = os.urandom(32).hex()
-        tx = MockTx(0, tx_hash)
-        block = MockBlock(0, [tx_hash])
-        drv.add_block(block)
+        generator = MockBlockGenerator()
+        generator.generate([1], driver=drv)
 
         fltr_one = MockFilter('foo', brk_hard=1)
         self.store.register(fltr_one)
@@ -110,30 +98,11 @@ class TestFilter(unittest.TestCase):
         with self.assertRaises(LockError):
             drv = MockDriver(store, target=1)
 
-#        drv.add_block(block)
-#
-#        tx_hash_one = os.urandom(32).hex()
-#        tx = MockTx(0, tx_hash_one)
-#        tx_hash_two = os.urandom(32).hex()
-#        tx = MockTx(1, tx_hash_two)
-#        block = MockBlock(1, [tx_hash_one, tx_hash_two])
-#        drv.add_block(block)
 
-#            drv.run(self.conn)
-
-
-    def test_driver_interrupt_resume(self):
+    def test_driver_interrupt_filter(self):
         drv = MockDriver(self.store, target=1)
-
-        tx_hash = os.urandom(32).hex()
-        tx = MockTx(0, tx_hash)
-        block = MockBlock(0, [tx_hash])
-        drv.add_block(block)
-
-        tx_hash = os.urandom(32).hex()
-        tx = MockTx(0, tx_hash)
-        block = MockBlock(1, [tx_hash])
-        drv.add_block(block)
+        generator = MockBlockGenerator()
+        generator.generate([1, 1], driver=drv)
 
         fltr_one = MockFilter('foo', brk=1)
         self.store.register(fltr_one)
@@ -147,5 +116,11 @@ class TestFilter(unittest.TestCase):
             drv.run(self.conn)
 
 
+    def test_driver_interrupt_sync(self):
+        generator = MockBlockGenerator()
+        drv = MockDriver(self.store, target=1)
+        generator.generate([1, 2], driver=drv)
+
+
 if __name__ == '__main__':
     unittest.main()