Add two testing utilities

posttroll/testing.py

@@ -0,0 +1,24 @@
+"""Testing utilities."""
+from contextlib import contextmanager
+
+@contextmanager
+def patched_subscriber_recv(messages):
+    """Patch the Subscriber object to return given messages."""
+    from unittest import mock
+    with mock.patch("posttroll.subscriber.Subscriber.recv", mock.Mock(return_value=messages)):
+        yield
+
+@contextmanager
+def patched_publisher():
+    """Patch the Subscriber object to return given messages."""
+    from unittest import mock
+    published = []
+
+    def fake_send(self, message):
+        published.append(message)
+
+    def noop(self, *args, **kwargs):
+        pass
+
+    with mock.patch.multiple("posttroll.publisher.Publisher", send=fake_send, start=noop, stop=noop):
+        yield published

posttroll/tests/test_testing.py

@@ -0,0 +1,11 @@
+from posttroll.testing import patched_publisher
+
+def test_fake_publisher():
+    from posttroll.publisher import create_publisher_from_dict_config
+
+    with patched_publisher() as messages:
+        pub = create_publisher_from_dict_config(dict(port=1979, nameservers=False))
+        pub.start()
+        pub.send("bla")
+        pub.stop()
+        assert "bla" in messages