Fix response ci header (#1244)

* add unit tests, which should fail

* fix CIDict

* moving CIDict to avoid circular imports

* fix unit tests

* use multidict for headers

* fix cookie

* add version constraint for multidict

* omit test coverage for __main__.py

* make flake8 happy

* consolidate check in for loop

* travisci retry build

tests/test_cookies.py

@@ -25,6 +25,7 @@ def test_cookies():
     assert response.text == 'Cookies are: working!'
     assert response_cookies['right_back'].value == 'at you'
 
+
 @pytest.mark.parametrize("httponly,expected", [
         (False, False),
         (True, True),

tests/test_response.py

@@ -64,6 +64,25 @@ def test_method_not_allowed():
     assert response.headers['Content-Length'] == '0'
 
 
+def test_response_header():
+    app = Sanic('test_response_header')
+    @app.get('/')
+    async def test(request):
+        return json({
+            "ok": True
+        }, headers={
+            'CONTENT-TYPE': 'application/json'
+        })
+
+    request, response = app.test_client.get('/')
+    assert dict(response.headers) == {
+        'Connection': 'keep-alive',
+        'Keep-Alive': '2',
+        'Content-Length': '11',
+        'Content-Type': 'application/json',
+    }
+
+
 @pytest.fixture
 def json_app():
     app = Sanic('json')