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.
'should not blow away user-entered text on successful reconnect to a controlled textarea',
          async () => {
            let changeCount = 0;
            await testUserInteractionBeforeClientRender(
              <ControlledTextArea onChange={() => changeCount++} />,
            );
            expect(changeCount).toBe(0);
          },
        );
        it('should not blow away user-selected value on successful reconnect to an uncontrolled select', () =>
          testUserInteractionBeforeClientRender(
            <select defaultValue="Hello">
              <option key="1" value="Hello">Hello</option>
              <option key="2" value="Goodbye">Goodbye</option>
            </select>,
          ));
        it('should not blow away user-selected value on successful reconnect to an controlled select', async () => {
          let changeCount = 0;
          await testUserInteractionBeforeClientRender(
            <ControlledSelect onChange={() => changeCount++} />,
          );
          expect(changeCount).toBe(0);
        });
      });
    });
  });
  describe('context', function() {
    let PurpleContext, RedContext;
    beforeEach(() => {
      class Parent extends React.Component {