Merge pull request #2865 from kirankoduru/2831-explicit-msg-for-scrapy-parse-callback

[MRG+1] Explicit message for scrapy parse callback

scrapy/spiders/__init__.py

@@ -87,7 +87,7 @@ class Spider(object_ref):
         return Request(url, dont_filter=True)
 
     def parse(self, response):
-        raise NotImplementedError
+        raise NotImplementedError('{}.parse callback is not defined'.format(self.__class__.__name__))
 
     @classmethod
     def update_settings(cls, settings):

tests/test_spider.py

@@ -429,3 +429,17 @@ class DeprecationTest(unittest.TestCase):
             self.assertEqual(len(requests), 1)
             self.assertEqual(requests[0].url, 'http://example.com/foo')
             self.assertEqual(len(w), 1)
+
+
+class NoParseMethodSpiderTest(unittest.TestCase):
+
+    spider_class = Spider
+
+    def test_undefined_parse_method(self):
+        spider = self.spider_class('example.com')
+        text = b'Random text'
+        resp = TextResponse(url="http://www.example.com/random_url", body=text)
+
+        exc_msg = 'Spider.parse callback is not defined'
+        with self.assertRaisesRegexp(NotImplementedError, exc_msg):
+            spider.parse(resp)