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Add test case that uses preceding render phase update
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acdlite committed Mar 16, 2019
commit 476b8db1671aa2b029523e75282ba3be1a3934fe
Original file line number Diff line number Diff line change
Expand Up @@ -2014,4 +2014,37 @@ describe('ReactHooksWithNoopRenderer', () => {
]);
expect(ReactNoop).toMatchRenderedOutput('2');
});

it('should update latest rendered reducer when a preceding state receives a render phase update', () => {
// Similar to previous test, except using a preceding render phase update
// instead of new props.
let dispatch;
function App() {
const [step, setStep] = useState(0);
const [shadow, _dispatch] = useReducer(() => step, step);
dispatch = _dispatch;

if (step < 5) {
setStep(step + 1);
}

Scheduler.yieldValue(`Step: ${step}, Shadow: ${shadow}`);
return shadow;
}

ReactNoop.render(<App />);
expect(Scheduler).toFlushAndYield([
'Step: 0, Shadow: 0',
'Step: 1, Shadow: 0',
'Step: 2, Shadow: 0',
'Step: 3, Shadow: 0',
'Step: 4, Shadow: 0',
'Step: 5, Shadow: 0',
]);
expect(ReactNoop).toMatchRenderedOutput('0');

act(() => dispatch());
expect(Scheduler).toFlushAndYield(['Step: 5, Shadow: 5']);
expect(ReactNoop).toMatchRenderedOutput('5');
});
});