Add ability to use FormRequest in contracts

docs/topics/contracts.rst

@@ -86,8 +86,11 @@ override three methods:
     .. method:: Contract.adjust_request_args(args)
 
         This receives a ``dict`` as an argument containing default arguments
-        for :class:`~scrapy.http.Request` object. Must return the same or a
-        modified version of it.
+        for request object. If ``formdata`` is in ``args``, then
+        :class:`~scrapy.http.FormRequest` object is created,
+        otherwise :class:`~scrapy.http.Request` is used.
+
+        Must return the same or a modified version of it.
 
     .. method:: Contract.pre_process(response)
 

scrapy/contracts/__init__.py

@@ -3,6 +3,7 @@ import re
 from functools import wraps
 from unittest import TestCase
 
+from scrapy import FormRequest
 from scrapy.http import Request
 from scrapy.utils.spider import iterate_spider_output
 from scrapy.utils.python import get_spec
@@ -57,7 +58,11 @@ class ContractsManager(object):
             # create and prepare request
             args.remove('self')
             if set(args).issubset(set(kwargs)):
-                request = Request(**kwargs)
+                if 'formdata' in kwargs:
+                    kwargs['method'] = 'POST'
+                    request = FormRequest(**kwargs)
+                else:
+                    request = Request(**kwargs)
 
                 # execute pre and post hooks in order
                 for contract in reversed(contracts):

tests/test_contracts.py

@@ -3,11 +3,12 @@ from unittest import TextTestResult
 from twisted.python import failure
 from twisted.trial import unittest
 
+from scrapy import FormRequest
 from scrapy.spidermiddlewares.httperror import HttpError
 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,
@@ -24,6 +25,14 @@ class ResponseMock(object):
     url = 'http://scrapy.org'
 
 
+class CustomFormContract(Contract):
+    name = 'custom_form'
+
+    def adjust_request_args(self, args):
+        args['formdata'] = {'name': 'scrapy'}
+        return args
+
+
 class TestSpider(Spider):
     name = 'demo_spider'
 
@@ -100,9 +109,16 @@ class TestSpider(Spider):
         """
         pass
 
+    def custom_form(self, response):
+        """
+        @url http://scrapy.org
+        @custom_form
+        """
+        pass
+
 
 class ContractsManagerTest(unittest.TestCase):
-    contracts = [UrlContract, ReturnsContract, ScrapesContract]
+    contracts = [UrlContract, ReturnsContract, ScrapesContract, CustomFormContract]
 
     def setUp(self):
         self.conman = ContractsManager(self.contracts)
@@ -202,3 +218,9 @@ class ContractsManagerTest(unittest.TestCase):
 
         self.assertFalse(self.results.failures)
         self.assertTrue(self.results.errors)
+
+    def test_form_contract(self):
+        spider = TestSpider()
+        request = self.conman.from_method(spider.custom_form, self.results)
+        self.assertEqual(request.method, 'POST')
+        self.assertIsInstance(request, FormRequest)