Overview

Node.js v18 introduced the experimental Test Runner module under node:test.

Writing tests which check the same function but with different inputs often results in writing the same tedious boilerplate code.

import test from "node:test";
import { strictEqual } from "assert";

// function to test
function addOne(num) {
	return num + 1;
}

test("given num is 1, should return 2", (t) => {
	strictEqual(addOne(1), 2);
});

test("given num is 2, should return 3", (t) => {
	strictEqual(addOne(2), 3);
});

test("given num is 3, should return 4", (t) => {
	strictEqual(addOne(3), 4);
});

Defining your test cases using testArray will help reduce the boilerplate code produced when writing multiple test() statements.

import { strictEqual } from "assert";
import testArray from "@wellers/testarray";

// function to test
function addOne(num) {
	return num + 1;
}

const tests = [
	{
		name: 'given num is 1, should return 2',
		args: {
			num: 1,
			result: 2
		}
	},
	{
		name: 'given num is 2, should return 3',		
		args: {
			num: 2,
			result: 3
		}
	},
	{
		name: 'given num is 3, should return 4',
		args: {
			num: 3,
			result: 4
		}
	}
];

testArray(tests, test => {
	strictEqual(addOne(test.num), test.result);
});

More involved examples are available here.

API

testArray(tests, fn) - Given an array of tests, execute a function on each test's args.

• tests - object[] - Array of tests.
  • name - string - Name of the test.
  • timeout - number - Timeout in ms for this specific test.
  • before - function or async function - Execute a function prior to execution of the test.
  • after - function or async function - Execute a function after the execution of the test.
  • concurrency - number - The number of tests that can be run at the same time. Default: 1.
  • only - boolean - Only execute this test. --test-only command-line option is required when running tests to use this option.
  • skip - boolean - Skip this test.
  • todo - boolean or string - If truthy, the test marked as TODO. If a string is provided, that string is displayed in the test results as the reason why the test is TODO.
  • args - object, function or async function - Definition of the test data which will be passed to the fn.
• fn - function(test) or async function(test) - Receives the test args returned on test.