It seems problematic to allow arbitary non-lowercase attribute on HTML nodes. Because the server has no ability to keep them case sensitive (HTML isn't). So they will end up different on the client.

We should probably warn if the attribute is not a known one *and* is not lowercase.
expect(changeCount).toBe(1);
          expect(e.checked).toBe(false);
        });
        itClientRenders('a controlled select', async render => {
          let changeCount = 0;
          const e = await render(
            <ControlledSelect onChange={() => changeCount++} />,
          );
          expect(changeCount).toBe(0);
          expect(e.value).toBe('Hello');
          
          e.value = 'Goodbye';
          ReactTestUtils.Simulate.change(e);
          expect(changeCount).toBe(1);
          expect(e.value).toBe('Goodbye');
        });
      });
      describe('user interaction with inputs before client render', function() {
        
        
        
        
        
        const testUserInteractionBeforeClientRender = async (
          element,
          initialValue = 'Hello',
          changedValue = 'Goodbye',
          valueKey = 'value',
        ) => {
          const field = await serverRender(element);