react-day-picker/src/formatters/formatWeekdayName.test.ts

Customizable Date Picker for React

import { es } from "date-fns/locale/es";

import { formatWeekdayName } from "./formatWeekdayName";

const date = new Date(2022, 10, 21);

test("should return the formatted weekday name", () => {
  expect(formatWeekdayName(date)).toEqual("Mo");
});

describe("when a locale is passed in", () => {
  test("should format using the locale", () => {
    expect(formatWeekdayName(date, { locale: es })).toEqual("lu");
  });
});