fix failing test by defaulting to empty array

src/diff/index.js

@@ -5,6 +5,7 @@ import { diffChildren } from './children';
 import { diffProps } from './props';
 import { assign, removeNode } from '../util';
 import options from '../options';
+import { toChildArray } from '..';
 
 /**
  * Diff two virtual nodes and apply proper changes to the DOM
@@ -165,7 +166,9 @@ export function diff(
 			tmp = c.render(c.props, c.state, c.context);
 			let isTopLevelFragment =
 				tmp != null && tmp.type == Fragment && tmp.key == null;
-			newVNode._children = isTopLevelFragment ? tmp.props.children : tmp;
+			newVNode._children = toChildArray(
+				isTopLevelFragment ? tmp.props.children : tmp
+			);
 
 			if (c.getChildContext != null) {
 				context = assign(assign({}, context), c.getChildContext());