Vitest setup for unit testing in Vue - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the function needed to define a test in Vitest.

Vue

import { [1] } from 'vitest';

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

Arender

Bmount

Cdescribe

Dtest

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'describe' instead of 'test' for a single test case.

Trying to import 'mount' which is from Vue Test Utils, not Vitest.

The test function is used to define a unit test in Vitest.

2fill in blank

medium

Complete the code to import the assertion function to check values in Vitest.

Vue

import { [1] } from 'vitest';

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

Acheck

Bassert

Cexpect

Dverify

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'assert' which is not part of Vitest's API.

Confusing with other testing libraries' assertion functions.

The expect function is used to write assertions in Vitest tests.

3fill in blank

hard

Fix the error in the Vitest test function declaration.

Vue

test('adds numbers', () => {
  const sum = 1 + 2;
  [1](sum).toBe(3);
});

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

Acheck

Bexpect

Cassert

Dverify

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent functions like 'check' or 'assert'.

Forgetting to wrap the value with expect.

The assertion function expect is used to check the test result.

4fill in blank

hard

Fill both blanks to create a Vitest test suite with a test case.

Vue

import { [1], [2] } from 'vitest';

describe('math tests', () => {
  test('multiply', () => {
    const result = 2 * 3;
    expect(result).toBe(6);
  });
});

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

Adescribe

Btest

Cexpect

Dmount

Attempts:

3 left

💡 Hint

Common Mistakes

Importing 'mount' which is unrelated to Vitest.

Mixing up 'expect' with test definition functions.

describe groups tests, and test defines a test case in Vitest.

5fill in blank

hard

Fill all three blanks to write a Vitest test that checks if a Vue component renders text.

Vue

import { [1], [2] } from 'vitest';
import { shallowMount } from '@vue/test-utils';
import HelloWorld from './HelloWorld.vue';

test('renders greeting', () => {
  const wrapper = shallowMount(HelloWorld);
  [3](wrapper.text()).toContain('Hello');
});

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

Atest

Bexpect

CshallowMount

Ddescribe

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'describe' instead of 'test' for the test case.

Not using 'expect' to check the component output.

test defines the test, expect asserts the output. shallowMount is imported separately.

Practice

1. What is the main purpose of Vitest when working with Vue projects?

easy

A. To run unit tests quickly and efficiently

B. To build and bundle Vue components

C. To style Vue components with CSS

D. To deploy Vue applications to servers

Solution

1. Step 1: Understand Vitest's role

   Vitest is a testing framework designed to run tests fast and provide feedback.

2. Step 2: Compare with other options

   Building, styling, and deploying are not testing tasks, so they don't match Vitest's purpose.

3. Final Answer:

   To run unit tests quickly and efficiently -> Option A

4. Quick Check:

   Vitest = fast unit testing [OK]

Hint: Vitest is for testing, not building or styling [OK]

Common Mistakes:

• Confusing Vitest with build tools
• Thinking Vitest handles styling
• Assuming Vitest deploys apps

2. Which of the following is the correct way to import Vue Test Utils in a Vitest test file?

easy

A. import mount from 'vue-test-utils';

B. import { mount } from '@vue/test-utils';

C. const mount = require('@vue/test-utils');

D. import { mount } from 'vitest/vue';

Solution

1. Step 1: Check correct import syntax

   Vue Test Utils exports mount as a named export, so use curly braces and the correct package name '@vue/test-utils'.

2. Step 2: Eliminate incorrect options

   import mount from 'vue-test-utils'; uses wrong package name and default import, C uses CommonJS require which is not standard ES modules, D uses wrong package name.

3. Final Answer:

   import { mount } from '@vue/test-utils'; -> Option B

4. Quick Check:

   Correct import = import { mount } from '@vue/test-utils'; [OK]

Hint: Use named imports with curly braces from '@vue/test-utils' [OK]

Common Mistakes:

• Using default import instead of named import
• Using require instead of import
• Wrong package name in import

3. Given this Vitest test code for a Vue component:

import { mount } from '@vue/test-utils';
import { describe, it, expect } from 'vitest';
import HelloWorld from './HelloWorld.vue';

describe('HelloWorld', () => {
  it('renders greeting', () => {
    const wrapper = mount(HelloWorld);
    expect(wrapper.text()).toContain('Hello');
  });
});

What will happen when this test runs?

medium

A. The test passes only if the component has a button

B. The test fails because mount is not imported correctly

C. The test passes if the component's text includes 'Hello'

D. The test throws a runtime error due to missing props

Solution

1. Step 1: Analyze the test logic

   The test mounts the HelloWorld component and checks if its text includes 'Hello'.

2. Step 2: Check for errors or conditions

   Mount is imported correctly, no props are required, and the test expects 'Hello' in text.

3. Final Answer:

   The test passes if the component's text includes 'Hello' -> Option C

4. Quick Check:

   Text includes 'Hello' = test passes [OK]

Hint: Check what the expect statement verifies in the test [OK]

Common Mistakes:

• Assuming mount import is wrong
• Thinking props are mandatory here
• Confusing test condition with button presence

4. You wrote this Vitest test but it fails with "ReferenceError: describe is not defined":

import { mount } from '@vue/test-utils';
import HelloWorld from './HelloWorld.vue';

describe('HelloWorld', () => {
  it('renders greeting', () => {
    const wrapper = mount(HelloWorld);
    expect(wrapper.text()).toContain('Hello');
  });
});

What is the most likely fix?

medium

A. Remove the mount import

B. Change describe to test and it to check

C. Wrap the test code inside a Vue component

D. Add import { describe, it, expect } from 'vitest'; at the top

Solution

1. Step 1: Identify missing imports

   The error says 'describe' is not defined, meaning it is not imported from Vitest.

2. Step 2: Add necessary imports

   Importing describe, it, and expect from 'vitest' fixes the error.

3. Final Answer:

   Add import { describe, it, expect } from 'vitest'; at the top -> Option D

4. Quick Check:

   Missing test functions import = add import [OK]

Hint: Always import test functions from 'vitest' [OK]

Common Mistakes:

• Assuming describe is globally available
• Changing test function names incorrectly
• Removing needed imports

5. You want to test a Vue component that uses a global plugin. Which Vitest setup step is necessary to ensure the plugin works during testing?

hard

A. Configure the test to mount the component with the plugin registered globally

B. Mock the plugin by replacing it with an empty object

C. Import the plugin inside the test file but do not register it

D. Run the test without mounting the component

Solution

1. Step 1: Understand plugin usage in tests

   Global plugins must be registered in the test mount options to behave like in the app.

2. Step 2: Choose correct setup

   Mounting with the plugin registered globally ensures the component can use it during the test.

3. Final Answer:

   Configure the test to mount the component with the plugin registered globally -> Option A

4. Quick Check:

   Global plugin = register in mount options [OK]

Hint: Register global plugins in mount options for tests [OK]

Common Mistakes:

• Mocking plugin without registering it
• Importing plugin but not registering
• Testing without mounting component