Question 73228 in Reactjs Question posted in
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How can I test this method with Jest? – Reactjs

import { format, getDaysInMonth, getMonth, getYear, isValid, parse } from "date-fns";

export class DateService {

  public getDaysInMonth(month?: Date) {
    return getDaysInMonth(month || new Date());
  }

How do I test it? How can I access the function implementation?

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2

Answers


  1. 0 
    jest
  .useFakeTimers()
  .setSystemTime(new Date('2020-01-01'));

describe("DateService", () => {
  test("getDaysInmonth", () => {
    // arrange
    const dateService = new DateService();
    const expected = new Date('2020-01-01');

    // act
    const actual = dateService.getDaysInMonth();
    
    // assert
    expect(actual).toEqual(expected);
  }
})
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  2. 0

    import the class:

    import { DateService } from "./DateService";

    setup your describe block and instantiate the DateService

    describe("DateService", () => {
  const dateService = new DateService();

    And then test results:

     it("should return the number of days", () => {
  const month = new Date(2022, 4); // May 2022
  const daysInMonth = dateService.getDaysInMonth(month);
  expect(daysInMonth).toBe(31);
});
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