diff --git a/spec/letsencrypt/configuration_spec.rb b/spec/letsencrypt/configuration_spec.rb
index e1520fd..a9c5225 100644
--- a/spec/letsencrypt/configuration_spec.rb
+++ b/spec/letsencrypt/configuration_spec.rb
@@ -3,43 +3,24 @@
 require 'rails_helper'
 
 RSpec.describe LetsEncrypt::Configuration do
+  subject(:config) { LetsEncrypt::Configuration.new }
+
   describe '#use_redis?' do
-    it 'reture is user enable save to redis value' do
-      subject.save_to_redis = true
-      expect(subject.use_redis?).to be_truthy
-    end
+    before { config.save_to_redis = true }
+
+    it { is_expected.to be_use_redis }
   end
 
   describe '#use_staging?' do
-    it 'return same value as #use_staging config attribute' do
-      subject.use_staging = true
-      expect(subject.use_staging?).to eq(subject.use_staging)
-    end
+    before { config.use_staging = true }
+
+    it { is_expected.to be_use_staging }
   end
 
   describe 'customize certificate model' do
-    before(:each) do
-      stub_const('OtherModel', Class.new(LetsEncrypt::Certificate))
-
-      OtherModel.after_update :success
-      OtherModel.class_eval do
-        def success
-          'success'
-        end
-      end
-
-      LetsEncrypt.config.certificate_model = 'OtherModel'
-      allow(LetsEncrypt).to receive(:certificate_model).and_return(OtherModel)
-      LetsEncrypt.certificate_model.create(
-        domain: 'example.com',
-        verification_path: '.well-known/acme-challenge/valid_path',
-        verification_string: 'verification'
-      )
-    end
+    before(:each) { config.certificate_model = 'OtherModel' }
     after { LetsEncrypt.config.certificate_model = 'LetsEncrypt::Certificate' }
-    it 'update data' do
-      expect_any_instance_of(OtherModel).to receive(:success)
-      LetsEncrypt.certificate_model.first.update(renew_after: 3.days.ago)
-    end
+
+    it { is_expected.to have_attributes(certificate_model: 'OtherModel') }
   end
 end