Blimp presubmit to check for unit tests on new .cc files.

blimp/PRESUBMIT.py

 # Copyright 2015 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.
 
 """Top-level presubmit script for blimp.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools.
 """
 
 import re
 
 BLIMP_SOURCE_FILES=(r'^blimp[\\/].*\.(cc|h)$',)
 
 def CheckChangeLintsClean(input_api, output_api):
   source_filter = lambda x: input_api.FilterSourceFile(
     x, white_list=BLIMP_SOURCE_FILES, black_list=None)
 
   return input_api.canned_checks.CheckChangeLintsClean(
       input_api, output_api, source_filter, lint_filters=[], verbose_level=1)
 
+def CheckNewFilesHaveTests(input_api, output_api):
+  unittest_files = set()
+  files_needing_unittest = set()
+
+  for source_file in input_api.AffectedFiles():
+    if source_file.Action() == 'A':
+      name = source_file.LocalPath()
+      if name.endswith('_unittest.cc'):
+        unittest_files.add(name)
+      elif name.endswith('.cc') and not name.endswith('test.cc'):
+        files_needing_unittest.add(name)
+
+  missing_unittest_files = []
+
+  for name in files_needing_unittest:
+    unittest_name = re.sub(r'\.cc$', '_unittest.cc', name)
+    if unittest_name not in unittest_files:
+      missing_unittest_files.append(name)
+
+  if missing_unittest_files:
+    message = 'The following new files are missing unit tests:'
+    return [output_api.PresubmitPromptWarning(message, missing_unittest_files)]
+  else:
+    return []
+
 def CheckChangeOnUpload(input_api, output_api):
   results = []
   results += CheckChangeLintsClean(input_api, output_api)
+  results += CheckNewFilesHaveTests(input_api, output_api)
   return results