any-toolkit

A toolkit of utility methods for generating random values in tests.

Motivation

Inspired by Test-Driven Development: Extensive Tutorial by Grzesiek Galezowski.

Using random values in tests makes them more resilient — tests that pass only for specific hard-coded inputs often hide assumptions. any-toolkit provides helpers that generate valid random values so your tests focus on behaviour, not data.

Installation

npm install any-toolkit

Usage

import { anyString, anyInteger, anyOf } from "any-toolkit";

it("should store and retrieve a user", () => {
  const name = anyString();
  const age = anyPositiveInteger({ max: 120 });
  const role = anyOf("admin", "editor", "viewer");
  // ...
});

Using vitest? See any-toolkit-vitest — a drop-in replacement that prints the generated values in the error output when a test fails.

API

anyBoolean()

Returns a random true or false.

anyDate(options?)

Returns a random Date.

| Option | Default | Description | |--------|---------|-------------| | from | new Date(0) (Unix epoch) | Lower bound | | to | new Date() (now) | Upper bound |

anyDate()                                          // between epoch and now
anyDate({ from: new Date(2020, 0, 1) })            // from 2020-01-01 until now
anyDate({ from: new Date(2020, 0, 1), to: new Date(2020, 11, 31) })

anyError(message?)

Returns a new Error with a random printable message, or the provided message.

anyError()              // Error with random message
anyError("boom")        // Error("boom")

anyFloat(options?)

Returns a random floating-point number.

| Option | Default | Description | |--------|---------|-------------| | min | Number.MIN_VALUE | Lower bound (inclusive) | | max | Number.MAX_VALUE | Upper bound (inclusive) |

anyFloat()                        // any float
anyFloat({ min: 10, max: 20 })    // float in [10, 20]
anyFloat({ min: -20, max: -10 })  // negative float

anyPercentage()

Returns a random float in [0, 1]. Shorthand for anyFloat({ min: 0, max: 1 }).

anyInteger(options?)

Returns a random safe integer.

| Option | Default | Description | |--------|---------|-------------| | min | Number.MIN_SAFE_INTEGER | Lower bound (inclusive) | | max | Number.MAX_SAFE_INTEGER | Upper bound (inclusive) |

anyInteger()                      // any safe integer
anyInteger({ min: 1, max: 100 }) // integer in [1, 100]

anyPositiveInteger(options?)

Returns a random integer ≥ 1.

| Option | Default | Description | |--------|---------|-------------| | max | Number.MAX_SAFE_INTEGER | Upper bound (inclusive) |

anyNegativeInteger(options?)

Returns a random integer ≤ −1.

| Option | Default | Description | |--------|---------|-------------| | min | Number.MIN_SAFE_INTEGER | Lower bound (inclusive) |

anyOf(...values)

Returns a random element from the provided arguments.

anyOf("a", "b", "c")          // one of "a", "b", or "c"
anyOf(1, 2, 3)                 // one of 1, 2, or 3

anyString(length?) / anyString(regexp)

Returns a random string of the given length (default 16), or a string matching a regular expression.

anyString()                          // 16-character random string
anyString(32)                        // 32-character random string
anyString(/[A-Z]{3}-\d{4}/)         // e.g. "XKM-0472"

anyPrintableString(length?)

Returns a random string of printable ASCII characters (codes 32–126). Default length: 16.

anyIdentifier(length?)

Returns a random string that is a valid JS/TS identifier ([a-zA-Z_][a-zA-Z0-9_]*). Default length: 16.

License

MIT