Add test for has_message_body helper function.

tests/test_helpers.py

@@ -0,0 +1,14 @@
+from sanic.helpers import has_message_body
+
+
+def test_has_message_body():
+    tests = (
+        (100, False),
+        (102, False),
+        (204, False),
+        (200, True),
+        (304, False),
+        (400, True),
+    )
+    for status_code, expected in tests:
+        assert has_message_body(status_code) is expected