add controller tests

spec/controllers/errors_controller_spec.rb

@@ -0,0 +1,25 @@
+require "rails_helper"
+
+describe ErrorsController, type: :controller do
+
+  describe "GET #not_found" do
+    it "returns not_found" do
+      get :not_found
+      expect(response).to have_http_status(404)
+    end
+  end
+
+  describe "GET #unprocessable" do
+    it "returns unprocessable" do
+      get :unprocessable
+      expect(response).to have_http_status(422)
+    end
+  end
+
+  describe "GET #internal_error" do
+    it "returns internal_error" do
+      get :internal_error
+      expect(response).to have_http_status(500)
+    end
+  end
+end