Procedure and expert link

spec/models/expert_spec.rb

@@ -0,0 +1,16 @@
+require 'rails_helper'
+
+RSpec.describe Expert, type: :model do
+  describe 'an expert could be add to a procedure' do
+
+    let(:procedure) { create(:procedure) }
+    let(:expert) { Expert.create }
+
+    before do
+      procedure.experts << expert
+      procedure.reload
+    end
+
+    it { expect(procedure.experts).to eq([expert]) }
+  end
+end