getting-started.md

Getting Started

Install

npm install --save-dev vitest-gwt

vitest is a peer dependency; install it if you have not already:

npm install --save-dev vitest

Version compatibility

vitest-gwt stays in lockstep with Vitest's major version. Match the major version of Vitest you run:

Vitest	vitest-gwt
4.x	4.x
3.x	3.x
2.x	2.x

Your first test

Import test from vitest-gwt (not vitest) and describe a test with given, when, and then:

import { describe } from "vitest";
import test from "vitest-gwt";

describe("addition", () => {
  test("adds two numbers", {
    given: {
      two_numbers,
    },
    when: {
      adding_them,
    },
    then: {
      the_sum_is_correct,
    },
  });
});

// Clause signatures are explained in Writing Tests.
function two_numbers() {
  this.a = 2;
  this.b = 3;
}

function adding_them() {
  this.result = this.a + this.b;
}

function the_sum_is_correct() {
  expect(this.result).toBe(5);
}

describe and expect come from Vitest directly; only the test function comes from vitest-gwt.

How a test runs

1. All given clauses run, in order.
2. All when clauses run, in order.
3. All then clauses run, in order.

A fresh Context object is created for each test and bound to every clause, so this inside any clause points at the same per-test state.

Next: Writing Tests.