Mocking database calls in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the mocking library for testing database calls.

Express

const [1] = require('sinon');

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

Ajest

Bexpress

Cmongoose

Dsinon

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of a mocking library.

Confusing 'mongoose' (database ORM) with mocking tools.

The sinon library is commonly used to mock functions and database calls in Express apps.

2fill in blank

medium

Complete the code to stub the database method findUser to return a fake user.

Express

const stub = sinon.[1](db, 'findUser').returns({ id: 1, name: 'Test User' });

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Astub

Bmock

Cspy

Dfake

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'mock' which is different from 'stub' in Sinon.

Using 'spy' which only observes calls but does not replace behavior.

The stub method replaces the original function with a fake one that returns specified data.

3fill in blank

hard

Fix the error in restoring the stub after the test to avoid side effects.

Express

stub.[1]();

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Areset

Bclear

Crestore

DresetHistory

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'reset' which only resets call history but does not restore original function.

Using 'clear' which is not a Sinon method.

The restore method returns the original function to its normal state after stubbing.

4fill in blank

hard

Fill both blanks to create a mock Express route that uses the stubbed database call and sends a JSON response.

Express

app.get('/user', async (req, res) => {
  const user = await db.[1]();
  res.[2](user);
});

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AfindUser

Bsend

Cjson

DgetUser

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send' instead of 'json' which may send data but not set JSON content type.

Using wrong database method name like 'getUser'.

The route calls the stubbed findUser method and sends the user data as JSON with res.json().

5fill in blank

hard

Fill all three blanks to write a test that stubs the database call, calls the route handler, and asserts the response.

Express

const stub = sinon.[1](db, 'findUser').returns({ id: 2, name: 'Mocked' });

await request(app).get('/user').expect(200).expect(res => {
  if (res.body.name !== [2]) throw new Error('Wrong user');
});
stub.[3]();

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

Astub

B'Mocked'

Crestore

Dmock

Attempts:

3 left

💡 Hint

Common Mistakes

Not restoring the stub after the test.

Checking for the wrong user name string.

Using 'mock' instead of 'stub' for replacing the function.

The test stubs findUser, expects the response to have the mocked name, and restores the stub after.