Format Failure Message JSON

This commit modifies the RSpec Matcher to use
[`JSON.pretty_generate`][docs] to improve the formatting of JSON bodies
and schemata that appear in failure messages.

Additionally, the `json-schema` provided error messages have been moved
to the top of the failure messages, so that the reasons for failure
appear above (potentially lengthy) JSON bodies.

[docs]: http://ruby-doc.org/stdlib-2.0.0/libdoc/json/rdoc/JSON.html#method-i-pretty_generate

NEWS.md

@@ -1,6 +1,8 @@
 master
 ======
 
+* Use `JSON.pretty_generate` to format error messages.
+
 0.6.0
 =====
 

lib/json_matchers/rspec.rb

@@ -12,38 +12,42 @@ def initialize(schema_name, **options)
 
     def failure_message(response)
       <<-FAIL.strip_heredoc
-      expected
+      #{validation_failure_message}
 
-      #{response.body}
+      ---
 
-      to match schema "#{schema_name}":
+      expected
 
-      #{schema_body}
+      #{pretty_json(response.body)}
 
-      ---
+      to match schema "#{schema_name}":
 
-      #{validation_failure_message}
+      #{pretty_json(schema_body)}
 
       FAIL
     end
 
     def failure_message_when_negated(response)
       <<-FAIL.strip_heredoc
-      expected
+      #{validation_failure_message}
 
-      #{response.body}
+      ---
 
-      not to match schema "#{schema_name}":
+      expected
 
-      #{schema_body}
+      #{pretty_json(response.body)}
 
-      ---
+      not to match schema "#{schema_name}":
 
-      #{validation_failure_message}
+      #{pretty_json(schema_body)}
 
       FAIL
     end
 
+    def pretty_json(json_string)
+      JSON.pretty_generate(JSON.parse(json_string.to_s))
+    end
+
     def schema_path
       JsonMatchers.path_to_schema(schema_name)
     end

spec/json_matchers/match_response_schema_spec.rb

@@ -72,15 +72,15 @@
 
     expect {
       expect(response_for("bar" => 5)).to match_response_schema("foo")
-    }.to raise_error(/{"bar":5}/)
+    }.to raise_formatted_error(%{{ "bar": 5 }})
   end
 
   it "contains the body in the failure message when negated" do
     create_schema("foo", { "type" => "array" })
 
     expect {
       expect(response_for([])).not_to match_response_schema("foo")
-    }.to raise_error(/\[\]/)
+    }.to raise_formatted_error("[ ]")
   end
 
   it "contains the schema in the failure message" do
@@ -89,7 +89,7 @@
 
     expect {
       expect(response_for("bar" => 5)).to match_response_schema("foo")
-    }.to raise_error(/#{schema.to_json}/)
+    }.to raise_formatted_error(%{{ "type": "array" }})
   end
 
   it "contains the schema in the failure message when negated" do
@@ -98,7 +98,7 @@
 
     expect {
       expect(response_for([])).not_to match_response_schema("foo")
-    }.to raise_error(/#{schema.to_json}/)
+    }.to raise_formatted_error(%{{ "type": "array" }})
   end
 
   it "does not fail when the schema matches" do
@@ -129,4 +129,10 @@
     expect(valid_response).to match_response_schema("collection")
     expect(invalid_response).not_to match_response_schema("collection")
   end
+
+  def raise_formatted_error(error_message)
+    raise_error { |error|
+      expect(error.message.squish).to include(error_message)
+    }
+  end
 end