title: What can impact the speed of tests ran with Jest?
body: <p>I got <code>Jest</code> working in my environment, but I'm fairly certain that it's running way slower than it's supposed to. </p>
  
  <p>Currently, I'm just running 2 tests that are copied from the Jest intro tutorials. One is <a href="https://facebook.github.io/jest/docs/getting-started.html#content" rel="noreferrer">a simple sum function</a>, and another is <a href="https://facebook.github.io/jest/docs/tutorial-react.html#dom-testing" rel="noreferrer">a simple checkbox example using <code>Enzyme</code></a>. They take on average about 10 seconds until they start running (showing <code>Determining test suites to run...</code> for that time), and then about another 10 seconds from that point onwards (once the timer starts). This seems absurdly long for such simple components... </p>
  
  <p>I tried setting my <code>testEnvironment</code> to <code>node</code> to speed things up, but it hasn't made much of a difference. </p>
  
  <p>So accordingly: </p>
  
  <p>1) Is this normal? </p>
  
  <p>2) If not - what can cause <code>Jest</code> to slow down like this? </p>
  
  <p><strong>Some potential factors?</strong></p>
  
  <p>1) I <em>am</em> running these tests within a larger <code>React</code> project that contains ~20 or so react components, but none of them are being referenced by any of the tests - so I don't think they should be impacting this. =/</p>
  
  <p>2) I'm using the <code>fileName.test.js</code> naming system to let <code>Jest</code> know where the test files are, instead of putting everything in a <code>__tests__</code> folder as per the tutorials. </p>