Add unit test. Fix the layout for non-UIView subclasses

YogaKit/Source/YGLayout.m

@@ -306,7 +306,8 @@ static YGSize YGMeasureView(
   UIView *view = (__bridge UIView*) YGNodeGetContext(node);
   CGSize sizeThatFits = CGSizeZero;
 
-  if ([view.subviews count] > 0) {
+  // Fix for https://github.com/facebook/yoga/issues/606
+  if (![view isMemberOfClass:[UIView class]] || [view.subviews count] > 0) {
     sizeThatFits = [view sizeThatFits:(CGSize) {
       .width = constrainedWidth,
       .height = constrainedHeight,

YogaKit/Tests/YogaKitTests.m

@@ -129,6 +129,16 @@
   XCTAssertEqual(longTextLabelSize.width + textBadgeView.yoga.intrinsicSize.width, containerSize.width);
 }
 
+- (void)testSizeThatFitsEmptyView
+{
+  UIView *view = [[UIView alloc] initWithFrame:CGRectMake(10, 10, 200, 200)];
+  view.yoga.isEnabled = YES;
+
+  const CGSize viewSize = view.yoga.intrinsicSize;
+  XCTAssertEqual(viewSize.height, 0);
+  XCTAssertEqual(viewSize.width, 0);
+}
+
 - (void)testPreservingOrigin
 {
   UIView *container = [[UIView alloc] initWithFrame:CGRectMake(0,0,50,75)];