Quick Start

This guide walks through the first forged test: a service that stores students.

1. The type under test

interface Student {
  name: string;
  age: number;
  birthday: Date;
}

There is nothing special about it — Forger works with interfaces, classes, and type aliases alike.

2. Forge instead of building

Before Forger, the test would start with stub data:

const student = { name: 'test', age: 20, birthday: new Date() }; // noise

With Forger it becomes:

import { Forger } from '@artstesh/forger';

describe('student.service', () => {
  it('save success', () => {
    const student = Forger.create<Student>()!;
    //
    const result = studentService.save(student);
    //
    expect(result).toBeTruthy();
  });
});

Forger.create<Student>() returns a fully populated student: a random name, a random age, a random date. The test is now about the behavior of save — nothing else.

3. Pin what matters with createWith

When a concrete value is the point of the test, pin it:

it('rejects underage students', () => {
  const student = Forger.createWith<Student>()
    .with(s => s.age = 15)
    .result()!;
  //
  expect(studentService.save(student)).toBe(false);
});

One with() call pins one property; everything else stays generated. Details in createWith.

4. Tune the generation

Numeric ranges, string length and charset, date windows, array sizes — all controlled by a single optional settings object:

const student = Forger.create<Student>({
  numberMax: 100,
  stringLength: 8,
  arrayLength: 5,
  dateMin: new Date(2000, 0, 1),
});

The full list of knobs lives in Settings.

5. What's next

How it works — the compile-time transformer and the runtime factories.
Supported types — what every type kind produces.
Cookbook — ready-made recipes for common test-data needs.

08 September 2026