added more to the spec test for creating a new link

spec/create_spec.rb

@@ -14,8 +14,13 @@ end
 describe "Submit API request to create new link" do
   include Rack::Test::Methods
   it "should return link data in json format" do
-    post '/create'
-    last_response.should be_ok
+    data = {
+      url: 'http://google.com'
+    }
+    res = post('/create', data.to_json, "CONTENT_TYPE" => "application/json")
+    expect(last_response).to be_ok
+    expect(JSON.parse(last_response.body)['url']).to eq(data[:url])
+    expect(JSON.parse(last_response.body)['code']).not_to eq(nil)
   end
 end