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.
) {
          
          expect(e.childNodes.length).toBe(5);
          expectTextNode(e.childNodes[0], 'a');
          expectTextNode(e.childNodes[2], 'b');
          expect(e.childNodes[3].childNodes.length).toBe(3);
          expectTextNode(e.childNodes[3].childNodes[0], 'c');
          expectTextNode(e.childNodes[3].childNodes[2], 'd');
          expectTextNode(e.childNodes[4], 'e');
        } else {
          expect(e.childNodes.length).toBe(4);
          expectTextNode(e.childNodes[0], 'a');
          expectTextNode(e.childNodes[1], 'b');
          expect(e.childNodes[2].childNodes.length).toBe(2);
          expectTextNode(e.childNodes[2].childNodes[0], 'c');
          expectTextNode(e.childNodes[2].childNodes[1], 'd');
          expectTextNode(e.childNodes[3], 'e');
        }
      });
    });
    describe('number children', function() {
      itRenders('a number as single child', async render => {
        const e = await render(<div>{3}</div>);
        expect(e.textContent).toBe('3');
      });
      
      itRenders('zero as single child', async render => {
        const e = await render(<div>{0}</div>);
        expect(e.textContent).toBe('0');
      });