Add more information when status assertion fail

Having the response output is useful to understand
why the status code doesn't match the expected one.

gabbi/case.py

@@ -36,6 +36,8 @@ import wsgi_intercept
 from gabbi import json_parser
 from gabbi import utils
 
+MAX_CHARS_OUTPUT = 2000
+
 REPLACERS = [
     'SCHEME',
     'NETLOC',
@@ -308,11 +310,13 @@ class HTTPTestCase(unittest.TestCase):
 
         # Decode and store response
         decoded_output = utils.decode_content(response, content)
-        content_type = response.get('content-type', '').lower()
+        self.content_type = response.get('content-type', '').lower()
         if (decoded_output and
-                ('application/json' in content_type or
-                 '+json' in content_type)):
+                ('application/json' in self.content_type or
+                 '+json' in self.content_type)):
             self.json_data = json.loads(decoded_output)
+        else:
+            self.json_data = None
         self.output = decoded_output
 
     def _run_test(self):
@@ -402,7 +406,37 @@ class HTTPTestCase(unittest.TestCase):
             statii = [stat.strip() for stat in expected_status.split('||')]
         else:
             statii = [expected_status.strip()]
-        self.assertIn(observed_status, statii)
+
+        self.assert_in_or_print_output(observed_status, statii)
+
+    def assert_in_or_print_output(self, expected, iterable):
+        if utils.not_binary(self.content_type):
+            if expected in iterable:
+                return
+
+            if self.json_data:
+                full_response = json.dumps(self.json_data, indent=2,
+                                           separators=(',', ': '))
+            else:
+                full_response = self.output
+
+            max_chars = os.getenv('GABBIT_MAX_CHARS_OUTPUT', MAX_CHARS_OUTPUT)
+            response = full_response[0:max_chars]
+            is_truncated = (len(response) != len(full_response))
+
+            if iterable == self.output:
+                msg = "'%s' not found in %s%s" % (
+                    expected, response,
+                    '\n...truncated...' if is_truncated else ''
+                )
+            else:
+                msg = "'%s' not found in %s, %sresponse:\n%s" % (
+                    expected, iterable,
+                    'truncated ' if is_truncated else '',
+                    response)
+            self.fail(msg)
+        else:
+            self.assertIn(expected, iterable)
 
 
 class ServerError(Exception):

gabbi/handlers.py

@@ -82,7 +82,7 @@ class StringResponseHandler(ResponseHandler):
 
     def action(self, test, expected, value=None):
         expected = test.replace_template(expected)
-        test.assertIn(expected, test.output)
+        test.assert_in_or_print_output(expected, test.output)
 
 
 class JSONResponseHandler(ResponseHandler):

gabbi/tests/test_handlers.py

@@ -13,6 +13,7 @@
 """Test response handlers.
 """
 
+import json
 import unittest
 
 from gabbi import case
@@ -35,19 +36,55 @@ class HandlersTest(unittest.TestCase):
 
     def test_response_strings(self):
         handler = handlers.StringResponseHandler(self.test_class)
+        self.test.content_type = "text/plain"
+        self.test.json_data = None
         self.test.test_data = {'response_strings': ['alpha', 'beta']}
         self.test.output = 'alpha\nbeta\n'
         self._assert_handler(handler)
 
     def test_response_strings_fail(self):
         handler = handlers.StringResponseHandler(self.test_class)
+        self.test.content_type = "text/plain"
+        self.test.json_data = None
         self.test.test_data = {'response_strings': ['alpha', 'beta']}
         self.test.output = 'alpha\nbta\n'
         with self.assertRaises(AssertionError):
             self._assert_handler(handler)
 
+    def test_response_strings_fail_big_output(self):
+        handler = handlers.StringResponseHandler(self.test_class)
+        self.test.content_type = "text/plain"
+        self.test.json_data = None
+        self.test.test_data = {'response_strings': ['alpha', 'beta']}
+        self.test.output = 'alpha\nbta\n' * 1000
+        with self.assertRaises(AssertionError) as cm:
+            self._assert_handler(handler)
+
+        msg = str(cm.exception)
+        self.assertEqual(2036, len(msg))
+
+    def test_response_strings_fail_big_payload(self):
+        handler = handlers.StringResponseHandler(self.test_class)
+        self.test.content_type = "application/json"
+        self.test.test_data = {'response_strings': ['foobar']}
+        self.test.json_data = {
+            'objects': [{'name': 'cw',
+                         'location': 'barn'},
+                        {'name': 'chris',
+                         'location': 'house'}] * 100
+        }
+        self.test.output = json.dumps(self.test.json_data)
+        with self.assertRaises(AssertionError) as cm:
+            self._assert_handler(handler)
+
+        msg = str(cm.exception)
+        self.assertEqual(2038, len(msg))
+        # Check the pprint of the json
+        self.assertIn('      "location": "house"', msg)
+
     def test_response_json_paths(self):
         handler = handlers.JSONResponseHandler(self.test_class)
+        self.test.content_type = "application/json"
         self.test.test_data = {'response_json_paths': {
             '$.objects[0].name': 'cow',
             '$.objects[1].location': 'house',
@@ -62,6 +99,7 @@ class HandlersTest(unittest.TestCase):
 
     def test_response_json_paths_fail_data(self):
         handler = handlers.JSONResponseHandler(self.test_class)
+        self.test.content_type = "application/json"
         self.test.test_data = {'response_json_paths': {
             '$.objects[0].name': 'cow',
             '$.objects[1].location': 'house',
@@ -77,6 +115,7 @@ class HandlersTest(unittest.TestCase):
 
     def test_response_json_paths_fail_path(self):
         handler = handlers.JSONResponseHandler(self.test_class)
+        self.test.content_type = "application/json"
         self.test.test_data = {'response_json_paths': {
             '$.objects[1].name': 'cow',
         }}