While there are a lot of popular test runners in node.js ecosystem, like jest, mocha etc. node has recently introduced a built in test runner available as test package in the standard library. The official documentation describe the usage, and it should look familiar to people coming from most popular testing libraries.

import { describe, it } from "node:test";
import assert from "node:assert"

describe('A thing', () => {
  it('should work', () => {
    assert.strictEqual(1, 1);
  });
});

However, one aspect that it does not handle currently is snapshot testing.

As popularised by Jest, snapshot testing is a convenient mechanism to ensure that certain computed values don't change across test runs by storing the result on first run and comparing with the stored value in subsequent runs. Jest docs explain the concept in more detail.

Fortuantely, using the library snap-shot-core we can easily integrate snapshot testing with node:test without needing to switch to another testing library.

import Snap from "snap-shot-core"

describe('User insertion', () => {
    it('inserts new row', async () => {
        await UserService.createUser({
            email: 'janedoe@example.com'
        })
        const user = await UserService.findByEmail('janedoe@example.com')
        Snap.core({
            what: user,
            file: __filename,
            specName: 'inserts new row'
        })
    })
})

This will write a snapshot file if not present, or validate against once if present.

Note that one caveat here is that, being a standalone library we needed to explicitly specify the specName.

If using the test function from node:test, we have access to the test name through testContext.name, which we can pass to this lib.

import Snap from "snap-shot-core"

test('user insertion', (testCtx) => {
    await UserService.createUser({
        email: 'janedoe@example.com'
    })
    const user = await UserService.findByEmail('janedoe@example.com')
    Snap.core({
        what: user,
        file: __filename,
        specName: testCtx.name
    })
})

However, for BDD style tests, we don't have the test context injected. One convenient solution to prevent the spec names from getting out of sync is to use named functions.

describe('User insertion', () => {
    it(async function insertsNewRow() { // <-- Spec name inferred from function name
        await UserService.createUser({
            email: 'janedoe@example.com'
        })
        const user = await UserService.findByEmail('janedoe@example.com')
        Snap.core({
            what: user,
            file: __filename,
            specName: insertsNewRow.name
        })
    })
})

Lastly, if our test files are ES modules, we won't have access to __filename. We can instead use the fileURLToPath utility.

import Snap from "snap-shot-core"
import { fileURLToPath } from 'url'

describe('User insertion', () => {
    it(async function insertsNewRow() {
        await UserService.createUser({
            email: 'janedoe@example.com'
        })
        const user = await UserService.findByEmail('janedoe@example.com')
        Snap.core({
            what: user,
            file: fileURLToPath(import.meta.url),
            specName: insertsNewRow.name
        })
    })
})