This is a potential bug reproduction: when using Jest to mock React components while using Typescript, the following error is produced:
FAIL src/__tests__/ParentComponent_test.tsx
● renders correctly
Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in. Check the render method of `ParentComponent`.
at invariant (node_modules/fbjs/lib/invariant.js:44:15)
at instantiateReactComponent (node_modules/react-test-renderer/lib/instantiateReactComponent.js:77:56)
at instantiateChild (node_modules/react-test-renderer/lib/ReactChildReconciler.js:44:28)
at node_modules/react-test-renderer/lib/ReactChildReconciler.js:71:16
at traverseAllChildrenImpl (node_modules/react-test-renderer/lib/traverseAllChildren.js:77:5)
at traverseAllChildrenImpl (node_modules/react-test-renderer/lib/traverseAllChildren.js:93:23)
at traverseAllChildren (node_modules/react-test-renderer/lib/traverseAllChildren.js:172:10)
at Object.instantiateChildren (node_modules/react-test-renderer/lib/ReactChildReconciler.js:70:7)
at ReactTestComponent._reconcilerInstantiateChildren (node_modules/react-test-renderer/lib/ReactMultiChild.js:187:41)
at ReactTestComponent.mountChildren (node_modules/react-test-renderer/lib/ReactMultiChild.js:226:27)
✕ renders correctly (14ms)
Test Suites: 1 failed, 1 total
Tests: 1 failed, 1 total
Snapshots: 0 total
Time: 0.78s
Ran all test suites.
console.error node_modules/fbjs/lib/warning.js:36
Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in. Check the render method of `ParentComponent`.
It contains an es6 directory with a minimal test setup using Babel which works, and a nearly identical typescript directory reproducing the problem.
To run the code in either the es6 or the typescript directory:
$ npm install
$ npm test