Cookbook

Copy-paste recipes for recurring test scenarios. All snippets assume import { should } from '@artstesh/it-should'; (plus Times where used).

A sorted API response

it('returns users ordered by age', () => {
  const users = service.getUsers();
  should().array(users).ordered({ by: (u) => u?.age });
});

A paginated list with a stable contract

it('returns exactly one page of active users', () => {
  const page = service.getActiveUsers(1);
  should().array(page).length(20)
    .containOnly((u) => u!.active);
});

"This field, exactly twice"

import { should, Times } from '@artstesh/it-should';

it('mentions the disclaimer twice', () => {
  should().string(body).contains('disclaimer', Times.twice());
});

Comparing DTOs with generated fields

it('maps the entity to the DTO', () => {
  should()
    .objects(actualDto, expectedDto)
    .ignoring('updatedAt', 'version')
    .equal();
});

The same data under different field names

should()
  .objects(apiResponse, domainModel)
  .map('first_name', 'firstName')
  .map('last_name', 'lastName')
  .equal();

A timestamp within a tolerance

it('stamps the event with the current time', () => {
  should().date(event.timestamp).equals(new Date(), 'minute'); // same minute is enough
});

Unique keys in a collection

should().array(rows).uniq((r) => r?.id); // no duplicate ids

No forbidden calls recorded

it('does not touch analytics during logout', () => {
  service.logout();
  should().array(analyticsSpy.calls).not.containBy((c) => c!.name === 'page_view');
});

Presence and absence

should().string(cache.get('key')).defined();        // cached
should().string(cache.get('removed')).not.defined(); // evicted

Behavior quirks and sharp edges: Caveats.
Recommended habits: Best Practices.
Every signature: API reference.

02 сентября 2026

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