Writing test cases in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the testing framework.

Node.js

const { test, expect } = require('[1]');

Drag options to blanks, or click blank then click option'

Alodash

Bexpress

Creact

Djest

Attempts:

3 left

💡 Hint

Common Mistakes

Using a library unrelated to testing like express or react.

Forgetting to import the testing functions.

We use jest as the testing framework here. It provides test and expect functions.

2fill in blank

medium

Complete the code to define a test case with a description.

Node.js

test('[1]', () => {
  expect(2 + 2).toBe(4);
});

Drag options to blanks, or click blank then click option'

AFetch data

BCheck addition

CRender component

DStart server

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated descriptions like 'Start server' for a math test.

Leaving the description empty.

The test description should explain what the test checks. Here, it checks addition, so 'Check addition' fits best.

3fill in blank

hard

Fix the error in the assertion to check if the value is true.

Node.js

test('Check boolean', () => {
  expect(true).[1](true);
});

Drag options to blanks, or click blank then click option'

AtoBeTruthy

BtoEqual

CtoBe

DtoBeTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using toBeTrue which does not exist in Jest.

Using toBeTruthy which checks truthiness, not exact true.

The correct Jest matcher to check exact equality is toBe. toBeTrue is not a valid Jest matcher.

4fill in blank

hard

Fill both blanks to create a test that checks if a function throws an error.

Node.js

test('Throws error', () => {
  expect(() => [1]()).[2]();
});

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AmyFunction

BtoThrow

CtoBe

DanotherFunction

Attempts:

3 left

💡 Hint

Common Mistakes

Using a matcher that does not check for errors like toBe.

Using a wrong function name.

The function to test is myFunction. To check if it throws an error, use the toThrow matcher.

5fill in blank

hard

Fill all three blanks to write a test that checks if an async function resolves with a value.

Node.js

test('Async resolves', async () => {
  const result = await [1]();
  expect(result).[2]([3]);
});

Drag options to blanks, or click blank then click option'

AfetchData

BtoEqual

C'success'

DgetData

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name that is not async.

Using a matcher that does not check equality.

Not passing the expected value correctly.

The async function is getData. We check if the result equals the string 'success' using toEqual.