import { Either, right, left } from '@/core/either'; function doSomething(shouldSuccess: boolean): Either { if (shouldSuccess) { return right(10); } return left('error'); } test('success result', () => { const successResult = doSomething(true); expect(successResult.isRight()).toBe(true); }); test('error result', () => { const errorResult = doSomething(false); expect(errorResult.isLeft()).toBe(true); });