Added unittests for run_slave

PRESUBMIT.py

 # Copyright (c) 2012 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 buildbot.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
 details on the presubmit API built into git cl.
 """
 
@@ skipping 108 matching lines @@
 
   recipe_modules_tests = input_api.glob(
       join('scripts', 'slave', 'recipe_modules', '*', 'tests'))
   for path in recipe_modules_tests:
     tests.extend(input_api.canned_checks.GetUnitTestsInDirectory(
         input_api,
         output_api,
         path,
         whitelist))
 
+  tests.extend(input_api.canned_checks.GetUnitTestsInDirectory(
+      input_api,
+      output_api,
+      input_api.os_path.join(
+          'slave', 'tests'),

[dsansome, 2016/10/12 03:54:04]

I'd put this on the line above

[ddoman1, 2016/10/12 20:08:17]

Done.

+      whitelist))
+
   with pythonpath(infra_path + sys.path):
     import common.master_cfg_utils  # pylint: disable=F0401
     # Fetch recipe dependencies once in serial so that we don't hit a race
     # condition where multiple tests are trying to fetch at once.
     output = input_api.RunTests([input_api.Command(
         name='recipes fetch',
         cmd=[input_api.python_executable,
              input_api.os_path.join('scripts', 'slave', 'recipes.py'), 'fetch'],
         kwargs={},
         message=output_api.PresubmitError,
@@ skipping 44 matching lines @@
 def CheckChangeOnUpload(input_api, output_api):
   return [] # Try-jobs/commit-queue do a better job of testing, faster.
 
 
 def CheckChangeOnCommit(input_api, output_api):
   output = CommonChecks(input_api, output_api)
   output.extend(ConditionalChecks(input_api, output_api))
   output.extend(CommitChecks(input_api, output_api))
   output.extend(BuildInternalCheck(output, input_api, output_api))
   return output