added validations to micropost model

app/models/micropost.rb

@@ -1,3 +1,5 @@
 class Micropost < ActiveRecord::Base
   belongs_to :user
+  validates :user_id, presence: true
+  validates :content, presence: true, length: { maximum: 140 }
 end

test/models/micropost_test.rb

@@ -1,7 +1,29 @@
 require 'test_helper'
 
 class MicropostTest < ActiveSupport::TestCase
-  # test "the truth" do
-  #   assert true
-  # end
+
+  def setup
+    @user = users(:michael)
+    # This code is not idiomatically correct.
+    @micropost = Micropost.new(content: "Lorem ipsum", user_id: @user.id)
+  end
+
+  test "should be valid" do
+    assert @micropost.valid?
+  end
+
+  test "user id should be present" do
+    @micropost.user_id = nil
+    assert_not @micropost.valid?
+  end
+
+  test "content should be present " do
+    @micropost.content = "   "
+    assert_not @micropost.valid?
+  end
+
+  test "content should be at most 140 characters" do
+    @micropost.content = "a" * 141
+    assert_not @micropost.valid?
+  end
 end