```ruby
require 'test_helper'

class AnswerTest < ActiveSupport::TestCase
  # test "the truth" do
  #   assert true
  # end
end
```

Write model tests for an answer.
user
```ruby
require 'test_helper'

class AnswerTest < ActiveSupport::TestCase
  def setup
    @answer = answers(:one)
  end

  test 'should be valid' do
    assert @answer.valid?
  end

  test 'response should be present' do
    @answer.response = ''
    assert_not @answer.valid?
  end

  test 'response should not be too long' do
    @answer.response = 'a' * 65_537
    assert_not @answer.valid?
  end

  test 'should have a question' do
    @answer.question = nil
    assert_not @answer.valid?
  end

  test "doesn't need a feedback" do
    @answer.feedback = nil
    assert @answer.valid?
  end
end
```
assistant