Documentation for <@ in json path values

While writing the documentation it was discovered an additional
test case was needed, so that is added here. It tests partial
chunks of JSON.

docs/source/jsonpath.rst

@@ -64,8 +64,23 @@ lead to difficult to read tests and it also indicates that your
 gabbi tests are being used to test your serializers and data models,
 not just your API interactions.
 
+It is also possible to read raw JSON from disk for either all or
+some of a JSON response::
+
+    response_json_paths:
+        $: @<data.json
+
+or::
+
+    response_json_paths:
+        $.pets: <@pets.json
+        $.pets[0]: <@cat.json
+
+Examples like this can be found in one of gabbi's `own tests`_.
+
 There are more JSONPath examples in :doc:`example` and in the
 `jsonpath_rw`_ and `jsonpath_rw_ext`_ documentation.
 
 .. _jsonpath_rw: http://jsonpath-rw.readthedocs.io/en/latest/
 .. _jsonpath_rw_ext: https://python-jsonpath-rw-ext.readthedocs.io/en/latest/
+.. _own tests: https://github.com/cdent/gabbi/blob/master/gabbi/tests/gabbits_intercept/data.yaml

gabbi/tests/gabbits_intercept/cat.json

@@ -0,0 +1,4 @@
+{
+    "type": "cat",
+    "sound": "meow"
+}

gabbi/tests/gabbits_intercept/data.yaml

@@ -58,3 +58,17 @@ tests:
       response_json_paths:
           foo['bár']: 1
           $: <@data.json
+
+    - name: partial json from disk
+      POST: /
+      request_headers:
+          content-type: application/json
+      data:
+          pets:
+              - type: cat
+                sound: meow
+              - type: dog
+                sound: woof
+      response_json_paths:
+          $.pets: <@pets.json
+          $.pets[0]: <@cat.json

gabbi/tests/gabbits_intercept/pets.json

@@ -0,0 +1,10 @@
+[
+    {
+        "type": "cat",
+        "sound": "meow"
+    },
+    {
+        "type": "dog",
+        "sound": "woof"
+    }
+]