diff --git a/microdot.py b/microdot.py
index cf874e2..a814436 100644
--- a/microdot.py
+++ b/microdot.py
@@ -166,9 +166,9 @@ class Response():
             self.headers['Set-Cookie'] = [http_cookie]
 
     def complete(self):
-        if not 'Content-Length' in self.headers:
+        if 'Content-Length' not in self.headers:
             self.headers['Content-Length'] = str(len(self.body))
-        if not 'Content-Type' in self.headers:
+        if 'Content-Type' not in self.headers:
             self.headers['Content-Type'] = 'text/plain'
 
     def write(self, stream):
diff --git a/tests/test_microdot.py b/tests/test_microdot.py
index 65ffd27..8db1ce0 100644
--- a/tests/test_microdot.py
+++ b/tests/test_microdot.py
@@ -27,7 +27,7 @@ class TestMicrodot(unittest.TestCase):
         self.assertTrue(fd.response.startswith(b'HTTP/1.0 200 OK\r\n'))
         self.assertIn(b'Content-Length: 3\r\n', fd.response)
         self.assertIn(b'Content-Type: text/plain\r\n', fd.response)
-        self.assertTrue(fd.response.endswith(b'\r\nfoo'))
+        self.assertTrue(fd.response.endswith(b'\r\n\r\nfoo'))
 
     def test_post_request(self):
         app = Microdot()
@@ -46,7 +46,7 @@ class TestMicrodot(unittest.TestCase):
         self.assertTrue(fd.response.startswith(b'HTTP/1.0 200 OK\r\n'))
         self.assertIn(b'Content-Length: 3\r\n', fd.response)
         self.assertIn(b'Content-Type: text/plain\r\n', fd.response)
-        self.assertTrue(fd.response.endswith(b'\r\nbar'))
+        self.assertTrue(fd.response.endswith(b'\r\n\r\nbar'))
 
     def test_before_after_request(self):
         app = Microdot()
@@ -82,7 +82,7 @@ class TestMicrodot(unittest.TestCase):
         self.assertIn(b'Set-Cookie: foo=bar\r\n', fd.response)
         self.assertIn(b'Content-Length: 3\r\n', fd.response)
         self.assertIn(b'Content-Type: text/plain\r\n', fd.response)
-        self.assertTrue(fd.response.endswith(b'\r\nbar'))
+        self.assertTrue(fd.response.endswith(b'\r\n\r\nbar'))
 
         mock_socket.clear_requests()
         fd = mock_socket.add_request('GET', '/baz')
@@ -92,7 +92,7 @@ class TestMicrodot(unittest.TestCase):
         self.assertIn(b'Set-Cookie: foo=bar\r\n', fd.response)
         self.assertIn(b'Content-Length: 3\r\n', fd.response)
         self.assertIn(b'Content-Type: text/plain\r\n', fd.response)
-        self.assertTrue(fd.response.endswith(b'\r\nbaz'))
+        self.assertTrue(fd.response.endswith(b'\r\n\r\nbaz'))
 
     def test_404(self):
         app = Microdot()
@@ -107,7 +107,7 @@ class TestMicrodot(unittest.TestCase):
         self.assertTrue(fd.response.startswith(b'HTTP/1.0 404 N/A\r\n'))
         self.assertIn(b'Content-Length: 9\r\n', fd.response)
         self.assertIn(b'Content-Type: text/plain\r\n', fd.response)
-        self.assertTrue(fd.response.endswith(b'\r\nNot found'))
+        self.assertTrue(fd.response.endswith(b'\r\n\r\nNot found'))
 
     def test_404_handler(self):
         app = Microdot()
@@ -126,7 +126,7 @@ class TestMicrodot(unittest.TestCase):
         self.assertTrue(fd.response.startswith(b'HTTP/1.0 200 OK\r\n'))
         self.assertIn(b'Content-Length: 3\r\n', fd.response)
         self.assertIn(b'Content-Type: text/plain\r\n', fd.response)
-        self.assertTrue(fd.response.endswith(b'\r\n404'))
+        self.assertTrue(fd.response.endswith(b'\r\n\r\n404'))
 
     def test_500(self):
         app = Microdot()
@@ -141,7 +141,7 @@ class TestMicrodot(unittest.TestCase):
         self.assertTrue(fd.response.startswith(b'HTTP/1.0 500 N/A\r\n'))
         self.assertIn(b'Content-Length: 21\r\n', fd.response)
         self.assertIn(b'Content-Type: text/plain\r\n', fd.response)
-        self.assertTrue(fd.response.endswith(b'\r\nInternal server error'))
+        self.assertTrue(fd.response.endswith(b'\r\n\r\nInternal server error'))
 
     def test_500_handler(self):
         app = Microdot()
@@ -160,7 +160,7 @@ class TestMicrodot(unittest.TestCase):
         self.assertTrue(fd.response.startswith(b'HTTP/1.0 501 N/A\r\n'))
         self.assertIn(b'Content-Length: 3\r\n', fd.response)
         self.assertIn(b'Content-Type: text/plain\r\n', fd.response)
-        self.assertTrue(fd.response.endswith(b'\r\n501'))
+        self.assertTrue(fd.response.endswith(b'\r\n\r\n501'))
 
     def test_exception_handler(self):
         app = Microdot()
@@ -179,4 +179,4 @@ class TestMicrodot(unittest.TestCase):
         self.assertTrue(fd.response.startswith(b'HTTP/1.0 501 N/A\r\n'))
         self.assertIn(b'Content-Length: 3\r\n', fd.response)
         self.assertIn(b'Content-Type: text/plain\r\n', fd.response)
-        self.assertTrue(fd.response.endswith(b'\r\n501'))
+        self.assertTrue(fd.response.endswith(b'\r\n\r\n501'))
diff --git a/tests/test_response.py b/tests/test_response.py
index 112d2fb..7e130ae 100644
--- a/tests/test_response.py
+++ b/tests/test_response.py
@@ -17,13 +17,11 @@ class TestResponse(unittest.TestCase):
         self.assertEqual(res.body, b'foo')
         fd = io.BytesIO()
         res.write(fd)
-        self.assertEqual(
-            fd.getvalue(),
-            b'HTTP/1.0 200 OK\r\n'
-            b'Content-Length: 3\r\n'
-            b'Content-Type: text/plain\r\n'
-            b'\r\n'
-            b'foo')
+        response = fd.getvalue()
+        self.assertIn(b'HTTP/1.0 200 OK\r\n', response)
+        self.assertIn(b'Content-Length: 3\r\n', response)
+        self.assertIn(b'Content-Type: text/plain\r\n', response)
+        self.assertTrue(response.endswith(b'\r\n\r\nfoo'))
 
     def test_create_from_string_with_content_length(self):
         res = Response('foo', headers={'Content-Length': '2'})
@@ -32,13 +30,11 @@ class TestResponse(unittest.TestCase):
         self.assertEqual(res.body, b'foo')
         fd = io.BytesIO()
         res.write(fd)
-        self.assertEqual(
-            fd.getvalue(),
-            b'HTTP/1.0 200 OK\r\n'
-            b'Content-Length: 2\r\n'
-            b'Content-Type: text/plain\r\n'
-            b'\r\n'
-            b'foo')
+        response = fd.getvalue()
+        self.assertIn(b'HTTP/1.0 200 OK\r\n', response)
+        self.assertIn(b'Content-Length: 2\r\n', response)
+        self.assertIn(b'Content-Type: text/plain\r\n', response)
+        self.assertTrue(response.endswith(b'\r\n\r\nfoo'))
 
     def test_create_from_bytes(self):
         res = Response(b'foo')
@@ -47,13 +43,11 @@ class TestResponse(unittest.TestCase):
         self.assertEqual(res.body, b'foo')
         fd = io.BytesIO()
         res.write(fd)
-        self.assertEqual(
-            fd.getvalue(),
-            b'HTTP/1.0 200 OK\r\n'
-            b'Content-Length: 3\r\n'
-            b'Content-Type: text/plain\r\n'
-            b'\r\n'
-            b'foo')
+        response = fd.getvalue()
+        self.assertIn(b'HTTP/1.0 200 OK\r\n', response)
+        self.assertIn(b'Content-Length: 3\r\n', response)
+        self.assertIn(b'Content-Type: text/plain\r\n', response)
+        self.assertTrue(response.endswith(b'\r\n\r\nfoo'))
 
     def test_create_empty(self):
         res = Response(headers={'X-Foo': 'Bar'})
@@ -62,13 +56,12 @@ class TestResponse(unittest.TestCase):
         self.assertEqual(res.body, b'')
         fd = io.BytesIO()
         res.write(fd)
-        self.assertEqual(
-            fd.getvalue(),
-            b'HTTP/1.0 200 OK\r\n'
-            b'X-Foo: Bar\r\n'
-            b'Content-Length: 0\r\n'
-            b'Content-Type: text/plain\r\n'
-            b'\r\n')
+        response = fd.getvalue()
+        self.assertIn(b'HTTP/1.0 200 OK\r\n', response)
+        self.assertIn(b'X-Foo: Bar\r\n', response)
+        self.assertIn(b'Content-Length: 0\r\n', response)
+        self.assertIn(b'Content-Type: text/plain\r\n', response)
+        self.assertTrue(response.endswith(b'\r\n\r\n'))
 
     def test_create_json(self):
         res = Response({'foo': 'bar'})
@@ -77,13 +70,11 @@ class TestResponse(unittest.TestCase):
         self.assertEqual(res.body, b'{"foo": "bar"}')
         fd = io.BytesIO()
         res.write(fd)
-        self.assertEqual(
-            fd.getvalue(),
-            b'HTTP/1.0 200 OK\r\n'
-            b'Content-Type: application/json\r\n'
-            b'Content-Length: 14\r\n'
-            b'\r\n'
-            b'{"foo": "bar"}')
+        response = fd.getvalue()
+        self.assertIn(b'HTTP/1.0 200 OK\r\n', response)
+        self.assertIn(b'Content-Length: 14\r\n', response)
+        self.assertIn(b'Content-Type: application/json\r\n', response)
+        self.assertTrue(response.endswith(b'\r\n\r\n{"foo": "bar"}'))
 
         res = Response([1, '2'])
         self.assertEqual(res.status_code, 200)
@@ -91,13 +82,11 @@ class TestResponse(unittest.TestCase):
         self.assertEqual(res.body, b'[1, "2"]')
         fd = io.BytesIO()
         res.write(fd)
-        self.assertEqual(
-            fd.getvalue(),
-            b'HTTP/1.0 200 OK\r\n'
-            b'Content-Type: application/json\r\n'
-            b'Content-Length: 8\r\n'
-            b'\r\n'
-            b'[1, "2"]')
+        response = fd.getvalue()
+        self.assertIn(b'HTTP/1.0 200 OK\r\n', response)
+        self.assertIn(b'Content-Length: 8\r\n', response)
+        self.assertIn(b'Content-Type: application/json\r\n', response)
+        self.assertTrue(response.endswith(b'\r\n\r\n[1, "2"]'))
 
     def test_create_from_other(self):
         res = Response(123)