Testing react components with redux-toolkit inside

Question

I have a component like this:

export const DetailsItem: FC = (): ReactElement => {
  const { isInEditMode } = useAppSelector(({ editMode }) => editMode);
  if (isInEditMode) {
    return <DetailsItemEdit />;
  }
  return <DetailsItemDisplay />;
};

and am trying to test it.

describe('DetailsItem', () => {
  it('should render DetailsItemDisplay component', () => {
    render(
      <Provider store={}> // I want to pass isInEditMode here.
        <DetailsItem />
      </Provider>,
    );

    screen.debug();
  });
});

The problem is, I somehow need to mock the store, to match my case. Any ideas how I should handle this?

I remember in my previous project I used a npm package to do this, but can't find it now, and can't remember how I did it, or what it was called

Answer 1

you can create a helper function for your tests to abstract the setup of the store/dependencies:

// import dependencies here:

function createTestWithStore(stateFromTest, component) {
  let reducer = { reducerA, reducerB };
  let preloadedState = merge(initialState, stateFromTest);
  let store = configureStore({
    reducer,
    preloadedState
  })
  return <Provider store={store}>{component}</Provider>
}

and use it in your tests:

describe('DetailsItem', () => {
  it('should render DetailsItemDisplay component with a single item', () => {
    let testState = { list: [{ id: 1, name: "John" }] };
    render(createTestWithStore(testState, <DetailsItem />));
    screen.debug();
  });

  it('should render DetailsItemDisplay component no item', () => {
    let testState = { list: [] };
    render(createTestWithStore(testState, <DetailsItem />));
    screen.debug();
  });
});

have a look in the "Writing Tests" page from Redux, it is part of the "Recommended practices for testing apps using Redux": https://redux.js.org/usage/writing-tests#connected-components