add expert factory

spec/factories/expert.rb

@@ -0,0 +1,14 @@
+FactoryBot.define do
+  sequence(:create_expert_email) { |n| "expert#{n}@expert.com" }
+
+  factory :expert do
+    transient do
+      email { generate(:expert_email) }
+      password { 'somethingverycomplated!' }
+    end
+
+    initialize_with do
+      User.create_or_promote_to_expert(email, password).expert
+    end
+  end
+end

spec/models/expert_spec.rb

@@ -1,7 +1,7 @@
 RSpec.describe Expert, type: :model do
   describe 'an expert could be add to a procedure' do
     let(:procedure) { create(:procedure) }
-    let(:expert) { Expert.create }
+    let(:expert) { create(:expert) }
 
     before do
       procedure.experts << expert