add user scaffold

spec/models/user_spec.rb

@@ -0,0 +1,36 @@
+require 'rails_helper'
+
+RSpec.describe User, type: :model do
+  describe 'validations' do
+    describe 'username' do
+      it 'presence' do
+        user = build(:user, username: nil)
+
+        expect(user).to_not be_valid
+      end
+
+      it 'uniqueness' do
+        create(:user, username: 'xpto')
+        user = build(:user, username: 'xpto')
+
+        expect(user).to_not be_valid
+      end
+
+      it 'max length 14' do
+        with_15_caracters = build(:user, username: 'asdfghjklzxcvhn')
+        with_14_caracters = build(:user, username: 'asdfghjklzxcvh')
+
+        expect(with_15_caracters).to_not be_valid
+        expect(with_14_caracters).to be_valid
+      end
+
+      it 'format' do
+        with_invalid_format = build(:user, username: 'asdfghjklzxcvh!')
+        with_valid_format = build(:user, username: 'asdfghjklzxcvh')
+
+        expect(with_invalid_format).to_not be_valid
+        expect(with_valid_format).to be_valid
+      end
+    end
+  end
+end