Add test for WeatherModel.set_ohm

spec/weather-model_spec.rb

@@ -6,7 +6,7 @@ RSpec.describe WeatherModel do
   include WeatherModel
   before do
     # start an ohm
-    Ohm.redis = Redic.new("redis://127.0.0.1:6379/5")
+    WeatherModel.set_ohm Redic.new("redis://127.0.0.1:6379/5")
     # run migration
     Dir[File.dirname(__FILE__) + '/../db/migrate/*.rb'].each { |file| require  file }
     ActiveRecord::Base.establish_connection(