basic short then test case

createUser.ts

import * as faker from "faker"
import { User } from "../../src/userService"

export const createUser = (data: Partial<User> = {}) : User => {
    const fakeData: User = {
        id: faker.datatype.uuid(),
        username: faker.name.findName(),
        email: faker.internet.email(),
        country: faker.address.country(),
        department: faker.company.companyName(),
        divisionName: faker.name.jobArea(),
    }

    return {
        ...fakeData,
        ...data,
    }
};

short-test-then-and-given.ts

import { updateUser } from "./userService"
import { createUser } from "../tests/helpers/createUser"

describe('UserService - updateUser', () => {
    it('should update department', () => {
        // GIVEN
        const user = createUser()
        const updateData = {
            department: 'IT Support',
        }
        // WHEN
        const currentUser = updateUser(user, updateData)

        // THEN
        expect(currentUser).toMatchObject({
            id: user.id,
            department: updateData.department,
        })
    })
})