test-assert-lite

A lightweight node:test and node:assert compatible library for browsers.

• From node:test: describe / it, test with t.test() subtests, before / after, skip and todo
• From node:assert: assert and strict, with ok, equal, deepStrictEqual, throws, rejects, match and more
• The same test file runs in both Node.js and the browser
• Under 32KB minified, under 11KB gzipped, no dependencies
• tacli and its browser runners run node:test test suites unchanged. They map node:test to this library

SYNOPSIS

BDD style with describe and it:

import {strict as assert} from "test-assert-lite/assert"
import {describe, it} from "test-assert-lite/test"

const parseQuery = (search) => Object.fromEntries(new URLSearchParams(search))
const buildQuery = (params) => new URLSearchParams(params).toString()

describe("buildQuery() from an object", () => {
    it("round-trips through parseQuery()", () => {
        const params = {q: "cat", page: "2"}
        assert.deepEqual(parseQuery("?" + buildQuery(params)), params)
    })
    it("appends to a URL", () => {
        const url = new URL("https://example.com/search")
        url.search = buildQuery({q: "cat"})
        assert.equal(url.href, "https://example.com/search?q=cat")
    })
})

See test-assert-lite.d.ts for the supported API.

The same test suite runs under node, and in a browser:

node --test test/query.test.mjs

# https://www.npmjs.com/package/test-assert-cli
tacli --serve test/query.test.mjs

# https://www.npmjs.com/package/webdriver-js-cli
webdriver-js --test test/query.test.mjs

# https://www.npmjs.com/package/playwright-js-cli
chromium-js --test test/query.test.mjs

test with subtests:

import {strict as assert} from "test-assert-lite/assert"
import {test} from "test-assert-lite/test"

test("URLSearchParams", async (t) => {
    const params = new URLSearchParams("a=1&b=2")
    await t.test("reads a key", () => {
        assert.equal(params.get("a"), "1")
    })
    await t.test("is null for a missing key", () => {
        assert.equal(params.get("c"), null)
    })
})

BROWSER MODULE

Tests can also go straight into a page, with no build step.

The minified build is an ES module. An import map maps the package's name to it on a CDN.

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/test-assert-cli/htdocs/styles/test-assert-lite.css">
<script type="importmap">
{
    "imports": {
        "test-assert-lite": "https://cdn.jsdelivr.net/npm/test-assert-lite/dist/test-assert-lite.min.js",
        "test-assert-lite/test": "https://cdn.jsdelivr.net/npm/test-assert-lite/exports/test.js",
        "test-assert-lite/assert": "https://cdn.jsdelivr.net/npm/test-assert-lite/exports/assert.js",
        "test-assert-lite/process": "https://cdn.jsdelivr.net/npm/test-assert-lite/exports/process.js",
        "test-assert-lite/session": "https://cdn.jsdelivr.net/npm/test-assert-lite/exports/session.js"
    }
}
</script>
<div id="output"></div>
<script type="module">
    import {describe, it} from "test-assert-lite/test"
    import {strict as assert} from "test-assert-lite/assert"
    import {run, session} from "test-assert-lite/session"

    // The report goes to console.log by default. Here it is rendered as HTML in the page.
    // session() comes before the first test is declared, and run() closes it.
    session({
        reporter: "html",
        output: html => document.getElementById("output").insertAdjacentHTML("beforeend", html),
    })

    describe("URL", () => {
        it("keeps the host", () => {
            assert.equal(new URL("https://example.com/a?b").host, "example.com")
        })
    })

    // run() starts every test registered so far and resolves once they are reported
    run().then(result => console.log(result.success ? "PASS" : "FAIL"))
</script>

Bundled tests in a page

Or bundle the suites with the library into one ES module, so the page needs no import map. An entry imports the suites and calls run().

// test/browser.mjs
import "./query.test.mjs"
import "./params.test.mjs"
import {run} from "test-assert-lite/session"

run().then(result => console.log(result.success ? "PASS" : "FAIL"))

// rollup.config.mjs
import {nodeResolve} from "@rollup/plugin-node-resolve"

export default {
    input: "test/browser.mjs",
    output: {
        file: "htdocs/scripts/tests.js",
        format: "es",
    },
    plugins: [nodeResolve()],
    treeshake: false,
}

<script type="module" src="./scripts/tests.js"></script>

The report goes to the console. The same bundle runs under node unchanged.

SEE ALSO

• https://www.npmjs.com/package/test-assert-lite
• https://www.npmjs.com/package/test-assert-cli
• https://www.npmjs.com/package/webdriver-js-cli
• https://www.npmjs.com/package/playwright-js-cli
• https://github.com/kawanet/test-assert-lite
• https://nodejs.org/api/test.html
• https://nodejs.org/api/assert.html