Jestでmoduleのstubを作る

簡易

code:usecases.ts

import { repository } from './repositories';

export function usecase() {

const result = repository();

return result * 10;

}

code:repositories.ts

export function repository() {

const result = db;

return result;

}

const db = 42;

code:usecases.test.ts

import { repository } from './repositories';

import { usecase } from './usecases';

jest.mock('./repositories.ts');

describe('', () => {

test('', () => {

(repository as jest.Mock).mockReturnValue(10);

const sut = usecase();

expect(sut).toEqual(100);

});

});