Make webhooks as separate modules with view and tests.

Create python packege for every webhook with view.py and tests.py

zerver/webhooks/helloworld/tests.py

@@ -0,0 +1,31 @@
+# -*- coding: utf-8 -*-
+from typing import Text
+from zerver.lib.test_classes import WebhookTestCase
+
+class HelloWorldHookTests(WebhookTestCase):
+    STREAM_NAME = 'test'
+    URL_TEMPLATE = "/api/v1/external/helloworld?&api_key={api_key}"
+    FIXTURE_DIR_NAME = 'hello'
+
+    # Note: Include a test function per each distinct message condition your integration supports
+    def test_hello_message(self):
+        # type: () -> None
+        expected_subject = u"Hello World"
+        expected_message = u"Hello! I am happy to be here! :smile:\nThe Wikipedia featured article for today is **[Marilyn Monroe](https://en.wikipedia.org/wiki/Marilyn_Monroe)**"
+
+        # use fixture named helloworld_hello
+        self.send_and_test_stream_message('hello', expected_subject, expected_message,
+                                          content_type="application/x-www-form-urlencoded")
+
+    def test_goodbye_message(self):
+        # type: () -> None
+        expected_subject = u"Hello World"
+        expected_message = u"Hello! I am happy to be here! :smile:\nThe Wikipedia featured article for today is **[Goodbye](https://en.wikipedia.org/wiki/Goodbye)**"
+
+        # use fixture named helloworld_goodbye
+        self.send_and_test_stream_message('goodbye', expected_subject, expected_message,
+                                          content_type="application/x-www-form-urlencoded")
+
+    def get_body(self, fixture_name):
+        # type: (Text) -> Text
+        return self.fixture_data("helloworld", fixture_name, file_type="json")