CODEWITHSUNDEEP
reactjsunit-testingjestjs
nim007
nim007

Reputation: 3058

How to test the catch block to have the rejected promise in Jest

How can I test the catch block of this action creator to reject the promise and to dispatch the error type & payload.

export const testMethod = async (dispatch: any) => {
  try {
     const result = await some API call
     await dispatch({
       payload: result,
       type: SUCCESS_TYPE
     });
     return "success";
  }
  catch(error){
     await dispatch({
       payload: error,
       type: ERROR_TYPE
     });
     return Promise.reject(error);
  }
}

This is how I did for the try block.

it("should test try block", async () => {
  jest
    .spyOn(window, "fetch")
    .mockReturnValueOnce(Promise.resolve({data: "something"}));
  const dispatch = jest.fn();
  const response = await testMethod()(dispatch);
  expect(response).toEqual("success");
  expect(dispatch.mock.calls.length).toBe(1);
  expect(dispatch.mock.calls[0]).toStrictEqual([{
    payload: response,
    type: SUCCESS_TYPE
  }]);
});

Similarly, I want to get full coverage on the catch block. Any help is greatly appreciated as I'm new to unit tests.

Upvotes: 0

Views: 2581

Answers (1)

Estus Flask
Estus Flask

Reputation: 222548

It should be:

  let error = new Error('foo');
  jest.spyOn(window, "fetch").mockRejectedValueOnce(error);
  await expect(testMethod()(dispatch)).rejects.toThrow(error);
  expect(dispatch.mock.calls.length).toBe(1);
  expect(dispatch.mock.calls[0]).toStrictEqual([{
    payload: error,
    type: ERROR_TYPE
  }]);

Upvotes: 2

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