Add --unexpected-failures flag to run_mojo_python_tests.

mojo/tools/run_mojo_python_tests.py

Index: mojo/tools/run_mojo_python_tests.py
diff --git a/mojo/tools/run_mojo_python_tests.py b/mojo/tools/run_mojo_python_tests.py
index 2bee0abd9d71115d57d41cfa18c7f6225a7723b2..c96aba36d2cd0f9c27b1929ddd1ae53f1f983755 100755
--- a/mojo/tools/run_mojo_python_tests.py
+++ b/mojo/tools/run_mojo_python_tests.py
@@ -5,21 +5,27 @@
 
 import optparse
 import os
+import re
 import sys
 import unittest
 
 
-# TODO(dpranke): crbug.com/364709 . We should add the ability to return
-# JSONified results data for the bots.
-
-
 def main():
   parser = optparse.OptionParser()
+  parser.usage = 'run_mojo_python_tests.py [options] [tests...]'
   parser.add_option('-v', '--verbose', action='count', default=0)
+  parser.add_option('--unexpected-failures', metavar='FILENAME', action='store',
+                    help=('path to write a list of any tests that fail '
+                          'unexpectedly.'))
+  parser.epilog = ('If --unexpected-failures is passed, a list of the tests '
+                   'that failed (one per line) will be written to the file. '
+                   'If no tests failed, the file will be truncated (empty). '
+                   'If the test run did not completely properly, or something '
+                   'else weird happened, any existing file will be left '
+                   'unmodified. '
+                   'If --unexpected-failures is *not* passed, any existing '
+                   'file will be ignored and left unmodified.')
   options, args = parser.parse_args()
-  if args:
-    parser.usage()
-    return 1
 
   chromium_src_dir = os.path.join(os.path.dirname(__file__),
                                   os.pardir,
@@ -27,14 +33,42 @@ def main():
 
   loader = unittest.loader.TestLoader()
   print "Running Python unit tests under mojo/public/tools/bindings/pylib ..."
-  suite = loader.discover(os.path.join(chromium_src_dir, 'mojo', 'public',
-                                       'tools', 'bindings', 'pylib'),
-                          pattern='*_unittest.py')
 
-  runner = unittest.runner.TextTestRunner(verbosity=(options.verbose+1))
+  pylib_dir = os.path.join(chromium_src_dir, 'mojo', 'public',
+                           'tools', 'bindings', 'pylib')
+  if args:
+    if not pylib_dir in sys.path:
+        sys.path.append(pylib_dir)
+    suite = unittest.TestSuite()
+    for test_name in args:
+      suite.addTests(loader.loadTestsFromName(test_name))
+  else:
+    suite = loader.discover(pylib_dir, pattern='*_unittest.py')
+
+  runner = unittest.runner.TextTestRunner(verbosity=(options.verbose + 1))
   result = runner.run(suite)
+
+  if options.unexpected_failures:
+    WriteUnexpectedFailures(result, options.unexpected_failures)
+
   return 0 if result.wasSuccessful() else 1
 
 
+def WriteUnexpectedFailures(result, path):
+
+  # This regex and UnitTestName() extracts the test_name in a way
+  # that can be handed back to the loader successfully.
+
+  test_description = re.compile("(\w+) \(([\w.]+)\)")
+
+  def UnitTestName(test):
+    m = test_description.match(str(test))
+    return "%s.%s" % (m.group(2), m.group(1))
+
+  with open(path, 'w') as fp:
+    for (test, _) in result.failures + result.errors:
+      fp.write(UnitTestName(test) + '\n')
+
+
 if __name__ == '__main__':
   sys.exit(main())