bots: Add tests for followup bot.

'followup' bot has different message handling behavior for
different messages.
For usual messages it calls 'send_message' function of
'BotHandlerApi' class.
For empty messages it calls 'send_reply' function of
'BotHandlerApi' class.

bots/followup/test_followup.py

@@ -0,0 +1,39 @@
+#!/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__))
+sys.path.insert(0, os.path.normpath(os.path.join(our_dir)))
+# 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 TestFollowUpBot(BotTestCase):
+    bot_name = "followup"
+
+    def test_bot(self):
+        expected_send_reply = {
+            "": 'Please specify the message you want to send to followup stream after @mention-bot'
+        }
+        self.check_expected_responses(expected_send_reply, expected_method='send_reply')
+
+        expected_send_message = {
+            "foo": {
+                'type': 'stream',
+                'to': 'followup',
+                'subject': 'foo_sender@zulip.com',
+                'content': 'from foo_sender@zulip.com: foo',
+            },
+            "I have completed my task": {
+                'type': 'stream',
+                'to': 'followup',
+                'subject': 'foo_sender@zulip.com',
+                'content': 'from foo_sender@zulip.com: I have completed my task',
+            },
+        }
+        self.check_expected_responses(expected_send_message, expected_method='send_message')