Fix crrev and add test coverage for the main function.

scripts/slave/recipe_modules/crrev/resources/crrev_client_test.py

 #!/usr/bin/python
 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import json
 import os
 import sys
 import unittest
 
 sys.path.insert(0, os.path.join(
     os.path.dirname(__file__), '..', '..', '..', '..'))
 import common.env
 common.env.Install()
 
 import mock
 import requests
 
 import crrev_client  # pylint: disable=relative-import
 
 
 @mock.patch('requests.get')
 class CrrevClientTest(unittest.TestCase):
 
+  def test_main(self, mock_get):
+    mock_response = mock.MagicMock()
+    response_data = {
+        'git_sha': 'e91f8875e590ddf00af267062fc1a9ec48658373',
+        'numbering_type': 'COMMIT_POSITION'
+    }
+    mock_response.text = json.dumps(response_data)
+    mock_get.return_value = mock_response
+    output = crrev_client.main([
+        'get_numbering',
+        '--params-file=test_params_file.json',
+    ])
+    self.assertEqual(json.dumps(response_data, indent=2), output)
+    self.assertEqual(mock_get.call_count, 1)
+
   def test_simple_get(self, mock_get):
     mock_response = mock.MagicMock()
     response_data = {
         'git_sha': 'e91f8875e590ddf00af267062fc1a9ec48658373',
         'numbering_type': 'COMMIT_POSITION'
     }
     mock_response.text = json.dumps(response_data)
     mock_get.return_value = mock_response
     params = [
         ('number', '375953'),
@@ skipping 28 matching lines @@
   def test_retry(self, mock_get):
     mock_get.side_effect = requests.RequestException
     with self.assertRaises(requests.RequestException):
       crrev_client.crrev_get('redirect/123456', params={}, attempts=3)
     self.assertEqual(3, mock_get.call_count)
 
 
 if __name__ == '__main__':
   unittest.main()