Fix/mqtt payload match (#295)

* Fix matching anything token in non-json MQTT payload

* Add extra test for anything token

* Update docs

docs/source/mqtt.md

@@ -114,6 +114,7 @@ The full list of keys for this block:
   serialize into JSON.
 - `qos`: QoS level for publishing. Defaults to 0 in paho-mqtt.
 
+
 ### Options for receiving MQTT messages
 
 The `mqtt_response` key gives a topic and payload which should be received by
@@ -126,6 +127,14 @@ that timeout period, it is considered a failure.
 If other messages on the same topic but with a different payload arrive in the
 meantime, they are ignored and a warning will be logged.
 
+```yaml
+    mqtt_response:
+      topic: /device/123/ping
+      json:
+        thing_1: abc
+        thing_2: 123
+```
+
 The keys which can be used:
 
 - `topic`: The MQTT topic to subcribe to
@@ -136,6 +145,18 @@ The keys which can be used:
 - `qos`: The level of QoS to subscribe to the topic with. This defaults to 1,
   and it is unlikely that you will need to ever set this value manually.
 
+While the `json` key will follow the same matching rules as
+HTTP JSON responses, The special 'anything' token can be used with the
+`payload` key just to check that there was _some_ response on a topic:
+
+```yaml
+    mqtt_response:
+      topic: /device/123/ping
+      payload: !anything
+```
+
+Other type tokens such as `!anyint` will _not_ work.
+
 ## Mixing MQTT tests and HTTP tests
 
 If the architecture of your program combines MQTT and HTTP, Tavern can
@@ -149,7 +170,7 @@ for it to say that a light has been turned on. When it receives this message, it
 updates a database so that each future request to get the state of the device
 will return the updated state.
 
-```
+```yaml
 ---
 
 test_name: Make sure posting publishes mqtt message

example/mqtt/test_mqtt.tavern.yaml

@@ -268,3 +268,42 @@ stages:
         lights: !anyint
       timeout: 3
       qos: 1
+
+---
+
+test_name: Test can handle anything token
+
+includes:
+  - !include common.yaml
+
+paho-mqtt: *mqtt_spec
+
+stages:
+  - name: Test checking for lights status with anyint
+    mqtt_publish:
+      topic: /device/123/status
+    mqtt_response:
+      topic: /device/123/status/response
+      json:
+        lights: !anything
+      timeout: 3
+      qos: 1
+
+---
+
+test_name: Test type token on non-json payload
+
+includes:
+  - !include common.yaml
+
+paho-mqtt: *mqtt_spec
+
+stages:
+  - name: Test checking for lights status with anyint
+    mqtt_publish:
+      topic: /device/123/status
+    mqtt_response:
+      topic: /device/123/status/response
+      payload: !anything
+      timeout: 3
+      qos: 1

tavern/_plugins/mqtt/response.py

@@ -6,6 +6,7 @@
 from tavern.util import exceptions
 from tavern.response.base import BaseResponse
 from tavern.util.dict_util import check_keys_match_recursive
+from tavern.util.loader import ANYTHING
 
 try:
     LoadException = json.decoder.JSONDecodeError
@@ -109,6 +110,9 @@ def _await_response(self):
                     logger.warning(
                         "Message had payload '%s' but we expected no payload"
                     )
+            elif payload is ANYTHING:
+                logger.info("Got message on %s matching !anything token", topic)
+                break
             elif msg.payload != payload:
                 if json_payload:
                     try:

tox-integration.ini

@@ -42,8 +42,8 @@ commands =
 
     mqtt: tavern-ci --stdout test_mqtt.tavern.yaml
     mqtt: python -c "from tavern.core import run; exit(run('test_mqtt.tavern.yaml', pytest_args=[]))"
-    mqtt_failures: tavern-ci --stdout test_mqtt_failures.tavern.yaml
-    mqtt_failures: python -c "from tavern.core import run; exit(run('test_mqtt_failures.tavern.yaml', pytest_args=[]))"
+    mqtt: tavern-ci --stdout test_mqtt_failures.tavern.yaml
+    mqtt: python -c "from tavern.core import run; exit(run('test_mqtt_failures.tavern.yaml', pytest_args=[]))"
 
     generic: tavern-ci --stdout test_fixtures.tavern.yaml
     generic: python -c "from tavern.core import run; exit(run('test_fixtures.tavern.yaml', pytest_args=[]))"