title: Testing in Scala
body: <p>I am new to Scala and mostly to JVM in general.</p>
  
  <p>There is a statement in the <a href="https://rads.stackoverflow.com/amzn/click/com/B01EX49FOU" rel="nofollow noreferrer" rel="nofollow noreferrer">book</a>:</p>
  
  <blockquote>
    <p>To provide descriptive error messages when assertions fail, ScalaTest
    analyses the expressions passed to each assert invocation <strong>at compile
    time</strong>.</p>
  </blockquote>
  
  <p>which confused me a lot.</p>
  
  <p>What does this actually mean? How can <code>ScalaTest</code> access compile time information?</p>