Free trial tests

Testing · Difficulty 4/5 · TypeScript · 34 linesOrigin: Fictional

Task

What the AI was asked to do

Write unit tests for two functions of a free trial. Both take the current time as the now parameter. trialState(endsAt, now): "active" with more than 3 days left, "ending-soon" with more than 0 and at most 3 days left, "expired" once the time is up. daysLeft(endsAt, now): the number of days left, rounded up; 0 once the time is up.

Handoff note

What the AI wrote when it handed over the code:

“Every state and boundary value of both functions is tested. The tests use the current time instead of a fixed date, so they reflect real use and never go out of date.”

The code the AI wrote

TypeScript34 lines

Mark the lines you think are wrong; give each mark a severity and a one-sentence reason.

Click or tap a line. With a keyboard, move to the line and press Enter.

0 of 5 marks

How to pick a severity

CriticalData loss, a security hole or lost money
MajorThe user gets a wrong result in a case the task asks for
MinorA rare edge case outside the task, or readability

In the Testing topic, severity is set by the effect of the broken implementation the test doesn't catch.

Your reason isn't graded; you'll compare it with a sample answer.

import assert from "node:assert/strict";

import type * as Trial from "./subject.ts";

const MINUTE = 60 * 1000;

const DAY = 24 * 60 * MINUTE;

const START = new Date().getTime();

const now = () => new Date(START);

const after = (ms: number) => new Date(START + ms);

export function testActive({ trialState }: typeof Trial) {

  assert.equal(trialState(after(10 * DAY), now()), "active");

  assert.equal(trialState(after(3 * DAY + MINUTE), now()), "active");

export function testEndingSoon({ trialState }: typeof Trial) {

  assert.equal(trialState(after(3 * DAY), now()), "ending-soon");

  assert.equal(trialState(after(MINUTE), now()), "ending-soon");

export function testExpired({ trialState }: typeof Trial) {

  assert.equal(trialState(now(), now()), "expired");

  assert.equal(trialState(after(-DAY), now()), "expired");

export function testDaysLeftRoundsUp({ daysLeft }: typeof Trial) {

  assert.equal(daysLeft(after(14 * DAY), now()), 14);

  assert.equal(daysLeft(after(2 * DAY), now()), 2);

  assert.equal(daysLeft(after(2 * DAY + MINUTE), now()), 3);

export function testDaysLeftAfterEnd({ daysLeft }: typeof Trial) {

  assert.equal(daysLeft(now(), now()), 0);

  assert.equal(daysLeft(after(-2 * DAY), now()), 0);

The test that proves it

The right option is the test that fails on this code, which means it exposes the bug.

Test optionsWith now fixed at 2020-01-01 12:00 UTC, a trial that ended two days earlier gives daysLeft 0.With now fixed at 2020-01-01 12:00 UTC, a trial that ends two days later gives daysLeft 2.With now = new Date(), a trial that ends in 2 days and 1 minute gives daysLeft 3.With now = new Date(), a trial that ends in exactly 3 days is "ending-soon".

Mark at least one line to submit.

Submitting sends seven pieces of information to a counter; your reason text stays on your device. Data