VerifierFactory Reference

should() returns the VerifierFactory singleton — the only entry point of the library.

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

should().number(5).positive();

Factory methods

Method	Examined value	Returns
`array<T>(entry: (T \\| null \\| undefined)[] \\| null \\| undefined)`	an array	`ArrayVerifier<T>`
`number(entry: number \\| null \\| undefined)`	a number	`NumberVerifier`
`string(entry: string \\| null \\| undefined)`	a string	`StringVerifier`
`date(entry: Date \\| string \\| null \\| undefined)`	a date or ISO string	`DateVerifier`
`objects<T extends {}, P extends {}>(entry: T, other: P)`	two objects	`ObjectsVerifier<T, P>`

Method	Passes when	Failure message
`true(entry: any): void`	entry is truthy — not `false`, `0`, `''`, `null`, `undefined`, `NaN`	`The entry expected to be true.`
`false(entry: any): void`	entry is falsy	`The entry expected to be false.`

Both are terminal: they return void and have no not form. See General Assertions.

Every verifier returned above inherits:

Member	Behavior
`not` (property)	inverts every following check in the chain
`defined()`	passes when the entry is not `null`/`undefined`; otherwise throws `The entry is not defined.`

The rules for null/undefined entries under not are documented in Concepts.

02 сентября 2026