title: What is the purpose of a `transient do` block in FactoryBot factories?
body: <p>What is the purpose of <code>transient do</code> in FactoryBot factories?</p>
  <p>I've seen a lot of factories that begin with something like below.</p>
  <pre><code>factory :car do
    owner nil
    other_attribute nil
  end
  ...
  </code></pre>
  <p>I've found some information on this blog:<br />
  <a href="https://web.archive.org/web/20180403000920/http://blog.thefrontiergroup.com.au/2014/12/using-factorygirl-easily-create-complex-data-sets-rails/" rel="noreferrer">Using FactoryGirl to easily create complex data sets in Rails</a></p>
  <p>But I still don't fully understand how and why to do this. My experience with FactoryBot is minimal.</p>
  <p>Could anyone with some experience using FactoryBot share some insight?</p>