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(field[valueKey]).toBe(initialValue);
          
          field[valueKey] = changedValue;
          resetModules();
          
          const clientField = await renderIntoDom(
            element,
            field.parentNode,
            true,
          );
          
          
          
          expect(clientField === field).toBe(true);
          
          expect(clientField[valueKey]).toBe(changedValue);
        };
        it('should not blow away user-entered text on successful reconnect to an uncontrolled input', () =>
          testUserInteractionBeforeClientRender(
            <input defaultValue="Hello" />,
          ));
        it('should not blow away user-entered text on successful reconnect to a controlled input', async () => {
          let changeCount = 0;
          await testUserInteractionBeforeClientRender(
            <ControlledInput onChange={() => changeCount++} />,
          );
          
          
          
          expect(changeCount).toBe(0);