testsuite: Add tests for helloworld bot in contrib_bots.

Add test file 'test_helloworld.py'.

contrib_bots/bots/helloworld/test_helloworld.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+
+from __future__ import absolute_import
+from __future__ import print_function
+
+import os
+import sys
+
+our_dir = os.path.dirname(os.path.abspath(__file__))
+# For dev setups, we can find the API in the repo itself.
+if os.path.exists(os.path.join(our_dir, '..')):
+    sys.path.insert(0, '..')
+from bots_test_lib import BotTestCase
+
+class TestHelloWorldBot(BotTestCase):
+    bot_name = "helloworld"
+
+    def test_bot(self):
+        self.assert_bot_output(
+            {'content': "foo", 'type': "private", 'sender_email': "foo"},
+            "beep boop"
+        )
+        self.assert_bot_output(
+            {'content': "Hi, my name is abc", 'type': "stream", 'display_recipient': "foo", 'subject': "foo"},
+            "beep boop"
+        )
+        self.assert_bot_output(
+            {'content': "", 'type': "stream", 'display_recipient': "foo", 'subject': "foo"},
+            "beep boop"
+        )