Summary - Testing basics

Combine node:test, assert and mock to write a calculator test.

Summary - Testing basics

In this group you learned Node.js's built-in testing tools: the node:test framework, assert assertions, grouping with describe and it, before/after hooks, and fake functions with mock. Now we will combine them in a calculator test.

Structure: a describe("calculator") group with a before hook for setup, it("add") and it("subtract") tests using assert.equal, and a mock.fn() fake logger. This is a small example of what a real project's test file looks like. Tests are run with node --test file.js; the output shows a TAP-style report.

Exercise Write the calculator test

Import test, describe, before and mock from node:test, and also node:assert. Define function add(a, b) { return a + b; }. Create a fake logger with const log = mock.fn();. Write describe("calculator", () => { before(() => {}); test("add", () => { assert.equal(add(2, 3), 5); }); }). Print with console.log("Calculator test ready, mock: " + log.mock.calls.length).

Show example solution

const { test, describe, before, mock } = require("node:test");
const assert = require("node:assert");
function add(a, b) { return a + b; }
const log = mock.fn();
describe("calculator", () => {
  before(() => {});
  test("add", () => {
    assert.equal(add(2, 3), 5);
  });
});
console.log("Calculator test ready, mock: " + log.mock.calls.length);

Test yourself

What is the correct way to add setup to a test group?
```
describe('x', () => { /* ... */ })
```
- Adding before() inside describe
- Printing with console.log
- Calling test() outside the group
- assert.equal kullanmamak
Show answer

Adding before() inside describe — The before hook runs setup before the group.
Match each concept to its role

test

Defines a single test
assert.equal

Compares two values
describe

Groups tests
mock.fn

Creates a fake function

Complete the multi-import

const { test, describe, before, ____ } = require("node:test");

Show answer

const { test, describe, before, mock } = require("node:test");

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