Add missing truncate() call on BytesIO object (#52)

* When subsequent payload to be pushed by mocket was shorter than previous
one, additional data were dumped. This was because BytesIO object had
the longer length; calling truncate() on the BytesIO object solves this
problem

Author: toudi

mocket/mocket.py

@@ -199,6 +199,7 @@ def sendall(self, data, *args, **kwargs):
 
         self.fd.seek(0)
         self.fd.write(response)
+        self.fd.truncate()
         self.fd.seek(0)
 
     def recv(self, buffersize, flags=None):

tests/main/test_mocket.py

@@ -74,6 +74,25 @@ def test_getresponse(self):
     def test_empty_getresponse(self):
         entry = MocketEntry(('localhost', 8080), [])
         self.assertEqual(entry.get_response(), encode_to_bytes(''))
+        
+    @mocketize
+    def test_subsequent_recv_requests_have_correct_length(self):
+        Mocket.register(
+            MocketEntry(
+                ('localhost', 80),
+                [
+                    b'Long payload',
+                    b'Short'
+                ]
+            )
+        )
+        _so = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        _so.connect(('localhost', 80))
+        _so.sendall(b'first\r\n')
+        assert _so.recv(4096) == b'Long payload'
+        _so.sendall(b'second\r\n')
+        assert _so.recv(4096) == b'Short'
+        _so.close()
 
 
 class MocketizeTestCase(TestCase):