Follow up from https://github.com/facebook/react/pull/11616.

Here's one I found. These two invariants:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L330-L343

are in a function that's behind a DEV block:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L447-L449

I don't think this is intentional, but need to verify.

There may be more. I'll use this issue to track while https://github.com/facebook/react/pull/11616 preserves existing behavior.
},
          };
        },
      };
      let e = await render(threeDivIterable);
      let parent = e.parentNode;
      expect(parent.childNodes.length).toBe(3);
      expect(parent.childNodes[0].tagName).toBe('DIV');
      expect(parent.childNodes[1].tagName).toBe('DIV');
      expect(parent.childNodes[2].tagName).toBe('DIV');
    });
    itRenders('emptyish values', async render => {
      let e = await render(0);
      expect(e.nodeType).toBe(TEXT_NODE_TYPE);
      expect(e.nodeValue).toMatch('0');
      
      
      expect((await render(<div>{''}</div>)).textContent).toBe('');
      expect(await render(<React.Fragment />)).toBe(null);
      expect(await render([])).toBe(null);
      expect(await render(false)).toBe(null);
      expect(await render(true)).toBe(null);
      expect(await render(undefined)).toBe(null);
      expect(await render([[[false]], undefined])).toBe(null);
    });
  });
  describe('property to attribute mapping', function() {
    describe('string properties', function() {
      itRenders('simple numbers', async render => {
        const e = await render(<div width={30} />);