We missed this because Flow wasn't being run properly on Travis but now that it is, it's clear that #7716 introduced a bunch of new Flow failures. Most of these shouldn't be too bad and I like to say "you break it you buy it" so this one is for you @Aweary :)

There were a couple other pre-existing Flow issues that @vjeux is going to fix, so mostly this should just be the TestRenderer issues.

let beforeNode;
  if (node.parentNode === parentNode &&
      node.previousSibling === referenceNode) {
    return;
  }
  if (referenceNode == null) {
    
    beforeNode = parentNode.firstChild;
  } else {
    
    beforeNode = referenceNode.nextSibling;
  }
  if (beforeNode && beforeNode.previousSibling !== node) {
    
    
    invariant(
      node !== beforeNode,
      'ReactART: Can not insert node before itself'
    );
    node.injectBefore(beforeNode);