title: ES5 exported function not recognized
body: <p>I got this math.js:</p>
  
  <pre><code>const sum = (a, b) =&gt; a + b
  const mul = (a, b) =&gt; a * b
  
  export default { sum, mul }
  </code></pre>
  
  <p>then in math.test.js:</p>
  
  <pre><code>const { sum, mul } = require('./math')
  
  test('Adding 1 + 1 equals 2', () =&gt; {
    expect(sum(1, 1)).toBe(2)
  })
  
  test('Multiplying 1 * 1 equals 1', () =&gt; {
    expect(mul(1, 1)).toBe(1)
  })
  </code></pre>
  
  <p>I got this error from jest:</p>
  
  <pre><code>? Adding 1 + 1 equals 2
  
    TypeError: sum is not a function
  
      5 | })
      6 | test('Adding 1 + 1 equals 2', () =&gt; {
    &gt; 7 |   expect(sum(1, 1)).toBe(2)
      8 | })
      9 |
  </code></pre>
  
  <p>If I import those function in the test file, jest runs fine.
  Can't understand proper way to take external function in ES5.</p>