PRESUBMIT: Enforce tracker prefix for all BUG entries

Changed function definition from private to public. This was needed to test the function and to maintain the consistency.

BUG=webrtc:8197
NOTRY=True
R=kjellander@webrtc.org

Review-Url: https://codereview.webrtc.org/3010153002 .
Cr-Commit-Position: refs/heads/master@{#19831}

presubmit_test.py

@@ -0,0 +1,39 @@
+import unittest
+
+import PRESUBMIT
+from presubmit_test_mocks import MockInputApi, MockOutputApi
+
+
+class CheckBugEntryField(unittest.TestCase):
+  def testCommitMessageBugEntryWithNoError(self):
+    mock_input_api = MockInputApi()
+    mock_output_api = MockOutputApi()
+    mock_input_api.change.BUG = 'webrtc:1234'
+    errors = PRESUBMIT.CheckCommitMessageBugEntry(mock_input_api,
+                                                   mock_output_api)
+    self.assertEqual(0, len(errors))
+
+  def testCommitMessageBugEntryReturnError(self):
+    mock_input_api = MockInputApi()
+    mock_output_api = MockOutputApi()
+    mock_input_api.change.BUG = 'webrtc:1234,webrtc=4321'
+    errors = PRESUBMIT.CheckCommitMessageBugEntry(mock_input_api,
+                                                   mock_output_api)
+    self.assertEqual(1, len(errors))
+    self.assertEqual(('Bogus BUG entry: webrtc=4321. Please specify'
+                      ' the issue tracker prefix and the issue number,'
+                      ' separated by a colon, e.g. webrtc:123 or'
+                      ' chromium:12345.'), str(errors[0]))
+
+  def testCommitMessageBugEntryIsNone(self):
+    mock_input_api = MockInputApi()
+    mock_output_api = MockOutputApi()
+    mock_input_api.change.BUG = 'None'
+    errors = PRESUBMIT.CheckCommitMessageBugEntry(mock_input_api,
+                                                   mock_output_api)
+    self.assertEqual(0, len(errors))
+
+
+if __name__ == '__main__':
+  unittest.main()
+