AndrewSouthpaw / jest-default-props-eager-eval

jest-default-props-eager-eval

defaultProps in React seem to be eagerly evaluated, even if the component is not used.

I'm testing component Foo, which renders a Button. I imported this Button through an index.js file that contains both Button and Date.

In my test for Foo, I mock moment to return a function, expecting the usual invocation of moment(). However, in Date, it uses moment differently: moment.utc(). This shouldn't matter, except that it's being used inside defaultProps, which appears to evaluate when Date gets roped into the testing environment. See the error stack trace:

  ● Test suite failed to run

    TypeError: _moment2.default.utc is not a function
      
      at Object.<anonymous> (src/module_a/date.jsx:50:31)
      at Object.<anonymous> (src/module_a/index.js:10:13)
      at Object.<anonymous> (src/module_b/foo.jsx:18:17)
      at Object.<anonymous> (src/module_b/__tests__/foo.test.jsx:18:12)

With the default props in Date commented out, the test runs fine.