Nuxt•4d ago

Mocking a plugin

Is it possible to mock a plugin which is imported using useNuxtApp() in a component which is being unit tested?

6 Replies

Hi @Tobberoth. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave: ---------------------- Yes, it's possible to mock a plugin that's imported using useNuxtApp() in a component being unit tested. In Nuxt 3, you can use the mockNuxtImport utility from @nuxt/test-utils/runtime to mock the Nuxt imports, including plugins accessed via useNuxtApp(). Here's how you can approach this: 1. First, use mockNuxtImport to mock the useNuxtApp function:

import { mockNuxtImport } from '@nuxt/test-utils/runtime'

// Create a mock of useNuxtApp with your plugin
mockNuxtImport('useNuxtApp', () => {
  return () => ({
    // Mock your plugin here
    $yourPlugin: {
      someMethod: vi.fn(),
      someProperty: 'mocked value'
    }
    // Add other properties that useNuxtApp would normally return
  })
})

// Your tests here

import { mockNuxtImport } from '@nuxt/test-utils/runtime'

// Create a mock of useNuxtApp with your plugin
mockNuxtImport('useNuxtApp', () => {
  return () => ({
    // Mock your plugin here
    $yourPlugin: {
      someMethod: vi.fn(),
      someProperty: 'mocked value'
    }
    // Add other properties that useNuxtApp would normally return
  })
})

// Your tests here

If you need different implementations between tests, you can use vi.hoisted to create and expose your mocks:

import { vi } from 'vitest'
import { mockNuxtImport } from '@nuxt/test-utils/runtime'

const { useNuxtAppMock } = vi.hoisted(() => {
  return {
    useNuxtAppMock: vi.fn(() => ({
      $yourPlugin: {
        someMethod: vi.fn(),
        someProperty: 'mocked value'
      }
    }))
  }
})

mockNuxtImport('useNuxtApp', () => {
  return useNuxtAppMock
})

// Then, inside a test you can change the implementation
useNuxtAppMock.mockImplementation(() => ({
  $yourPlugin: {
    someMethod: vi.fn().mockReturnValue('different value'),
    someProperty: 'different mocked value'
  }
}))

import { vi } from 'vitest'
import { mockNuxtImport } from '@nuxt/test-utils/runtime'

const { useNuxtAppMock } = vi.hoisted(() => {
  return {
    useNuxtAppMock: vi.fn(() => ({
      $yourPlugin: {
        someMethod: vi.fn(),
        someProperty: 'mocked value'
      }
    }))
  }
})

mockNuxtImport('useNuxtApp', () => {
  return useNuxtAppMock
})

// Then, inside a test you can change the implementation
useNuxtAppMock.mockImplementation(() => ({
  $yourPlugin: {
    someMethod: vi.fn().mockReturnValue('different value'),
    someProperty: 'different mocked value'
  }
}))

Remember that mockNuxtImport can only be used once per mocked import per test file, as it's a macro that gets transformed to vi.mock, which is hoisted in Vitest as mentioned in the documentation. When testing components that use these plugins, you can use mountSuspended from @nuxt/test-utils/runtime to mount your component within the Nuxt environment:

import { mountSuspended } from '@nuxt/test-utils/runtime'
import YourComponent from '~/components/YourComponent.vue'

it('tests component with mocked plugin', async () => {
  const component = await mountSuspended(YourComponent)
  // Your assertions here
})

import { mountSuspended } from '@nuxt/test-utils/runtime'
import YourComponent from '~/components/YourComponent.vue'

it('tests component with mocked plugin', async () => {
  const component = await mountSuspended(YourComponent)
  // Your assertions here
})

Make sure your test file is properly set up to use the Nuxt environment, either by naming it with .nuxt.spec.ts extension or by adding the // @vitest-environment nuxt comment at the top of your test file. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•4d ago

<@184996700883124225> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

TobberothOP•4d ago

@kapa.ai Mocking useNuxtApp() does not seem to be a viable option, I get an error that nuxtApp.deferHydration() is not a function.

kapa.ai•4d ago

Let me check the knowledge base for you again. One moment! :books: ---------------------- I understand the issue you're facing with mocking useNuxtApp(). The error about nuxtApp.deferHydration() not being a function suggests that your mock is missing some essential functionality that Nuxt expects. Instead of completely mocking useNuxtApp(), a better approach would be to use runWithContext to ensure the proper Nuxt context is maintained. Here are a few alternative approaches: Option 1: Use mockNuxtImport for specific plugins or composables Rather than mocking the entire useNuxtApp(), you can mock just the specific plugin or functionality you need:

import { mockNuxtImport } from '@nuxt/test-utils/runtime'

// Mock a specific plugin or composable that your component uses
mockNuxtImport('useMyPlugin', () => {
  return () => ({
    someMethod: vi.fn(),
    someProperty: 'mocked value'
  })
})

import { mockNuxtImport } from '@nuxt/test-utils/runtime'

// Mock a specific plugin or composable that your component uses
mockNuxtImport('useMyPlugin', () => {
  return () => ({
    someMethod: vi.fn(),
    someProperty: 'mocked value'
  })
})

Option 2: Use vi.hoisted with a more complete mock If you still need to mock useNuxtApp(), ensure you include all the necessary functions:

import { vi } from 'vitest'
import { mockNuxtImport } from '@nuxt/test-utils/runtime'

const { useNuxtAppMock } = vi.hoisted(() => {
  return {
    useNuxtAppMock: vi.fn(() => ({
      // Include the required deferHydration function
      deferHydration: vi.fn(),
      // Your plugin
      $yourPlugin: {
        someMethod: vi.fn()
      },
      // Add other required properties
      runWithContext: (fn) => fn(),
      isHydrating: false
    }))
  }
})

mockNuxtImport('useNuxtApp', () => useNuxtAppMock)

import { vi } from 'vitest'
import { mockNuxtImport } from '@nuxt/test-utils/runtime'

const { useNuxtAppMock } = vi.hoisted(() => {
  return {
    useNuxtAppMock: vi.fn(() => ({
      // Include the required deferHydration function
      deferHydration: vi.fn(),
      // Your plugin
      $yourPlugin: {
        someMethod: vi.fn()
      },
      // Add other required properties
      runWithContext: (fn) => fn(),
      isHydrating: false
    }))
  }
})

mockNuxtImport('useNuxtApp', () => useNuxtAppMock)

Option 3: Use tryUseNuxtApp for safer access In your component, you might want to use tryUseNuxtApp instead of useNuxtApp if the plugin access is optional:

// In your component
const nuxtApp = tryUseNuxtApp()
if (nuxtApp) {
  // Use the plugin
}

// In your component
const nuxtApp = tryUseNuxtApp()
if (nuxtApp) {
  // Use the plugin
}

Then in your test, you can mock just the specific functionality:

mockNuxtImport('tryUseNuxtApp', () => {
  return () => ({
    $yourPlugin: {
      // Your mocked methods
    }
  })
})

mockNuxtImport('tryUseNuxtApp', () => {
  return () => ({
    $yourPlugin: {
      // Your mocked methods
    }
  })
})

The deferHydration function is part of Nuxt's internal hydration process, and mocking it incorrectly can cause issues. Using one of the approaches above should help you avoid this problem while still allowing you to test your component effectively. If you're still encountering issues, you might want to consider using the Nuxt testing environment which provides a more complete Nuxt context for your tests. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•4d ago

<@184996700883124225> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

TobberothOP•4d ago

Ok so it's not possible. nice waste of time there ^^

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Mocking a plugin

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