diff --git a/tests/test_contracts.py b/tests/test_contracts.py
index 1cea2afb7..078ef6e0d 100644
--- a/tests/test_contracts.py
+++ b/tests/test_contracts.py
@@ -5,7 +5,7 @@ from twisted.trial import unittest
 from scrapy.spiders import Spider
 from scrapy.http import Request
 from scrapy.item import Item, Field
-from scrapy.contracts import ContractsManager
+from scrapy.contracts import ContractsManager, Contract
 from scrapy.contracts.default import (
     UrlContract,
     ReturnsContract,
@@ -22,6 +22,21 @@ class ResponseMock(object):
     url = 'http://scrapy.org'
 
 
+class CustomSuccessContract(Contract):
+    name = 'custom_success_contract'
+
+    def adjust_request_args(self, args):
+        args['url'] = 'http://scrapy.org'
+        return args
+
+
+class CustomFailContract(Contract):
+    name = 'custom_fail_contract'
+
+    def adjust_request_args(self, args):
+        raise TypeError('Error in adjust_request_args')
+
+
 class TestSpider(Spider):
     name = 'demo_spider'
 
@@ -99,8 +114,34 @@ class TestSpider(Spider):
         pass
 
 
+class CustomContractSuccessSpider(Spider):
+    name = 'custom_contract_success_spider'
+
+    def parse(self, response):
+        """
+        @custom_success_contract
+        """
+        pass
+
+
+class CustomContractFailSpider(Spider):
+    name = 'custom_contract_fail_spider'
+
+    def parse(self, response):
+        """
+        @custom_fail_contract
+        """
+        pass
+
+
 class ContractsManagerTest(unittest.TestCase):
-    contracts = [UrlContract, ReturnsContract, ScrapesContract]
+    contracts = [
+        UrlContract,
+        ReturnsContract,
+        ScrapesContract,
+        CustomSuccessContract,
+        CustomFailContract
+    ]
 
     def setUp(self):
         self.conman = ContractsManager(self.contracts)
@@ -114,6 +155,9 @@ class ContractsManagerTest(unittest.TestCase):
         self.assertTrue(self.results.failures)
         self.assertFalse(self.results.errors)
 
+    def should_error(self):
+        self.assertTrue(self.results.errors)
+
     def test_contracts(self):
         spider = TestSpider()
 
@@ -185,3 +229,10 @@ class ContractsManagerTest(unittest.TestCase):
                 self.results)
         request.callback(response)
         self.should_fail()
+
+    def test_custom_contracts(self):
+        self.conman.from_spider(CustomContractSuccessSpider(), self.results)
+        self.should_succeed()
+
+        self.conman.from_spider(CustomContractFailSpider(), self.results)
+        self.should_error()