Fix failure message bug when response is string

- introduce `JsonMatchers::Payload` class to abstract away
  implementantion details of handling `response` or `String` arguments
- include test for failed string response
- fix `match_json_schema` typo in README

Author: sskylar

NEWS.md

@@ -1,6 +1,10 @@
 master
 ======
 
+* Fix error message for string responses. [#49]
+
+[#49]: https://github.com/thoughtbot/json_matchers/pull/49
+
 0.6.2
 =====
 

README.md

@@ -81,7 +81,7 @@ describe "GET /posts" do
     get posts_path, format: :json
 
     expect(response.status).to eq 200
-    expect(response.body).to match_json_schema("posts")
+    expect(response.body).to match_response_schema("posts")
   end
 end
 ```

lib/json_matchers/matcher.rb

@@ -1,4 +1,5 @@
 require "json-schema"
+require "json_matchers/payload"
 
 module JsonMatchers
   class Matcher
@@ -10,7 +11,7 @@ def initialize(schema_path, options = {})
     def matches?(response)
       JSON::Validator.validate!(
         schema_path.to_s,
-        json_from(response).to_s,
+        Payload.new(response).to_s,
         options,
       )
     rescue JSON::Schema::ValidationError => ex
@@ -28,14 +29,6 @@ def validation_failure_message
 
     attr_reader :schema_path, :options
 
-    def json_from(response)
-      if response.respond_to?(:body)
-        response.body
-      else
-        response
-      end
-    end
-
     def default_options
       JsonMatchers.configuration.options || {}
     end

lib/json_matchers/payload.rb

@@ -0,0 +1,23 @@
+module JsonMatchers
+  class Payload
+    def initialize(payload)
+      @payload = extract_json_string(payload)
+    end
+
+    def to_s
+      payload
+    end
+
+    private
+
+    attr_reader :payload
+
+    def extract_json_string(payload)
+      if payload.respond_to?(:body)
+        payload.body
+      else
+        payload
+      end
+    end
+  end
+end

lib/json_matchers/rspec.rb

@@ -1,4 +1,5 @@
 require "json_matchers"
+require "json_matchers/payload"
 
 module JsonMatchers
   class RSpec < SimpleDelegator
@@ -18,7 +19,7 @@ def failure_message(response)
 
 expected
 
-#{pretty_json(response.body)}
+#{pretty_json(response)}
 
 to match schema "#{schema_name}":
 
@@ -35,7 +36,7 @@ def failure_message_when_negated(response)
 
 expected
 
-#{pretty_json(response.body)}
+#{pretty_json(response)}
 
 not to match schema "#{schema_name}":
 
@@ -46,8 +47,10 @@ def failure_message_when_negated(response)
 
     private
 
-    def pretty_json(json_string)
-      JSON.pretty_generate(JSON.parse(json_string.to_s))
+    def pretty_json(response)
+      payload = Payload.new(response).to_s
+
+      JSON.pretty_generate(JSON.parse(payload))
     end
 
     def schema_path

spec/json_matchers/match_response_schema_spec.rb

@@ -22,20 +22,30 @@
     expect(response_for({})).not_to match_response_schema("foo_schema")
   end
 
-  it "validates a JSON string" do
-    create_schema("foo_schema", {
-      "type" => "object",
-      "required" => [
-        "id",
-      ],
-      "properties" => {
-        "id" => { "type" => "number" },
-      },
-      "additionalProperties" => false,
-    })
+  context "when JSON is a string" do
+    before(:each) do
+      create_schema("foo_schema", {
+        "type" => "object",
+        "required" => [
+          "id",
+        ],
+        "properties" => {
+          "id" => { "type" => "number" },
+        },
+        "additionalProperties" => false,
+      })
+    end
 
-    expect(response_for({ "id" => 1 }).body).
-      to match_response_schema("foo_schema")
+    it "validates when the schema matches" do
+      expect({ "id" => 1 }.to_json).
+        to match_response_schema("foo_schema")
+    end
+
+    it "fails with message when negated" do
+      expect {
+        expect({ "id" => "1" }.to_json).to match_response_schema("foo_schema")
+      }.to raise_formatted_error(%{{ "type": "number" }})
+    end
   end
 
   it "fails when the body contains a property with the wrong type" do