Add one unit test to activity model

test/models/activity_test.rb

 
 class ActivityTest < ActiveSupport::TestCase
   test "activity's author should exist" do
-    user = User.new(email: "test@test.com", username: "UserTest", password_digest: 'password')
+    user = User.new(email: "test@test.com", username: "UserTest", password_digest: '$6$12$password')
     activity = Activity.new(name: "Pyheatpump", description: "A software to control heat pumps", author: user)
     assert activity.valid?
   end
 
+  test "not valid if name does not exist" do
+    user = User.new(email: "test@test.com", username: "UserTest", password_digest: '$6$12$password')
+    activity = Activity.new(description: "A software to control heat pumps", author: user)
+    assert_not activity.valid?
+  end
+
   test "not valid if author does not exist" do
     activity = Activity.new(name: "Pyheatpump", description: "A software to control heat pumps", author: User.find_by_id(666))
     assert_not activity.valid?