It is a Jest-ism that shouldn't be in our open source package.
People using Jest can implement a similar pattern directly.
/**
 * @class ReactTestUtils
 */
/**
 * Simulates a top level event being dispatched from a raw event that occurred
 * on an `Element` node.
 * @param {number} topLevelType A number from `TopLevelEventTypes`
 * @param {!Element} node The dom to simulate an event occurring on.
 * @param {?Event} fakeNativeEvent Fake native event to use in SyntheticEvent.
 */
function simulateNativeEventOnNode(topLevelType, node, fakeNativeEvent) {
  fakeNativeEvent.target = node;
  ReactDOMEventListener.dispatchEvent(topLevelType, fakeNativeEvent);
}
/**
 * Simulates a top level event being dispatched from a raw event that occurred
 * on the `ReactDOMComponent` `comp`.
 * @param {Object} topLevelType A type from `BrowserEventConstants.topLevelTypes`.
 * @param {!ReactDOMComponent} comp
 * @param {?Event} fakeNativeEvent Fake native event to use in SyntheticEvent.
 */
function simulateNativeEventOnDOMComponent(
  topLevelType,
  comp,
  fakeNativeEvent,
) {
  simulateNativeEventOnNode(topLevelType, findDOMNode(comp), fakeNativeEvent);
}
function findAllInRenderedFiberTreeInternal(fiber, test) {