Second commit

app/models/user.rb

 class User < ApplicationRecord
   validates :name,  presence: true, length: { maximum: 50 }
-  validates :email, presence: true, length: { maximum: 255 }
+  VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i
+  validates :email, presence: true, length: { maximum: 255 },
+  format: { with: VALID_EMAIL_REGEX },
+  uniqueness: { case_sensitive: false }
 end

test/models/user_test.rb

 require "test_helper"
 
 class UserTest < ActiveSupport::TestCase
-
   def setup
     @user = User.new(name: "Example User", email: "user@example.com")
   end
@@ -10,6 +9,15 @@ class UserTest < ActiveSupport::TestCase
     assert @user.valid?
   end
 
+  test "name should be present" do
+    @user.name = ""
+    assert_not @user.valid?
+  end
+  test "email should be present" do
+    @user.email = "     "
+    assert_not @user.valid?
+  end
+  
   test "name should not be too long" do
     @user.name = "a" * 51
     assert_not @user.valid?
@@ -19,4 +27,27 @@ class UserTest < ActiveSupport::TestCase
     @user.email = "a" * 244 + "@example.com"
     assert_not @user.valid?
   end
+
+  test "email validation should accept valid addresses" do
+    valid_addresses = %w[user@example.com USER@foo.COM A_US-ER@foo.bar.org
+    first.last@foo.jp alice+bob@baz.cn]
+    valid_addresses.each do |valid_address|
+      @user.email = valid_address
+      assert @user.valid?, "#{valid_address.inspect} should be valid"
+    end
+  end
+  test "email validation should reject invalid addresses" do
+    invalid_addresses = %w[user@example,com user_at_foo.org user.name@example.
+    foo@bar_baz.com foo@bar+baz.com]
+    invalid_addresses.each do |invalid_address|
+      @user.email = invalid_address
+      assert_not @user.valid?, "#{invalid_address.inspect} should be invalid"
+    end
+  end
+  test "email addresses should be unique" do
+    duplicate_user = @user.dup
+    duplicate_user.email = @user.email.upcase
+    @user.save
+    assert_not duplicate_user.valid?
+  end
 end