msw/src/core/experimental/handlers-controller.test.ts

The industry standard for API mocking in JavaScript.

import { http } from '#http/http'
import { graphql } from '../../graphql'
import { ws } from '../../ws'
import {
  attachSiblingHandlers,
  getSiblingHandlers,
} from '../utils/internal/attach-sibling-handlers'
import {
  groupHandlersByKind,
  InMemoryHandlersController,
} from './handlers-controller'

const gql = graphql.link('*')

describe(groupHandlersByKind, () => {
  test('groups handlers attached as siblings of siblings', () => {
    const grandchildHandler = http.get('/grandchild', () => {})
    const childHandler = attachSiblingHandlers(
      http.get('/child', () => {}),
      [grandchildHandler],
    )
    const ownerHandler = attachSiblingHandlers(
      http.get('/owner', () => {}),
      [childHandler],
    )

    expect(groupHandlersByKind([ownerHandler]).request).toEqual([
      ownerHandler,
      childHandler,
      grandchildHandler,
    ])
  })

  test('groups nested siblings of a different kind into their own bucket', () => {
    const chat = ws.link('*')
    const wsHandler = chat.addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsHandler)
    const ownerHandler = attachSiblingHandlers(
      http.get('/owner', () => {}),
      [wsHandler],
    )

    const groups = groupHandlersByKind([ownerHandler])

    expect(groups.websocket).toEqual([wsHandler])
    expect(groups.request).toEqual([ownerHandler, upgradeHandler])
  })

  test('does not recurse infinitely given a cyclic sibling graph', () => {
    const handlerOne = http.get('/one', () => {})
    const handlerTwo = http.get('/two', () => {})
    attachSiblingHandlers(handlerOne, [handlerTwo])
    attachSiblingHandlers(handlerTwo, [handlerOne])

    expect(groupHandlersByKind([handlerOne]).request).toEqual([
      handlerOne,
      handlerTwo,
    ])
  })
})

describe('constructor', () => {
  test('places the sibling in its own kind bucket', () => {
    const wsHandler = ws.link('*').addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsHandler)

    const controller = new InMemoryHandlersController([wsHandler])

    expect(controller.getHandlersByKind('websocket')).toEqual([wsHandler])
    expect(controller.getHandlersByKind('request')).toEqual([upgradeHandler])
  })

  test('interleaves the sibling at the owner position when grouping by kind', () => {
    const httpOne = http.get('/', () => {})
    const wsHandler = ws.link('*').addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsHandler)
    const httpTwo = http.get('/', () => {})

    const controller = new InMemoryHandlersController([
      httpOne,
      wsHandler,
      httpTwo,
    ])

    expect(controller.getHandlersByKind('request')).toEqual([
      httpOne,
      upgradeHandler,
      httpTwo,
    ])
    expect(controller.getHandlersByKind('websocket')).toEqual([wsHandler])
  })

  test('extracts siblings from every owner in the input list', () => {
    const wsOne = ws.link('*').addEventListener('connection', () => {})
    const wsTwo = ws.link('*').addEventListener('connection', () => {})
    const [upgradeOne] = getSiblingHandlers(wsOne)
    const [upgradeTwo] = getSiblingHandlers(wsTwo)

    const controller = new InMemoryHandlersController([wsOne, wsTwo])

    expect(controller.getHandlersByKind('websocket')).toEqual([wsOne, wsTwo])
    expect(controller.getHandlersByKind('request')).toEqual([
      upgradeOne,
      upgradeTwo,
    ])
  })

  test('dedupes the shared upgrade sibling across multiple handlers from the same link', () => {
    const chat = ws.link('*')
    const wsOne = chat.addEventListener('connection', () => {})
    const wsTwo = chat.addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsOne)

    const controller = new InMemoryHandlersController([wsOne, wsTwo])

    expect(controller.getHandlersByKind('websocket')).toEqual([wsOne, wsTwo])
    expect(controller.getHandlersByKind('request')).toEqual([upgradeHandler])
  })
})

describe(InMemoryHandlersController.prototype.use, () => {
  test('prepends a handler to an empty controller', () => {
    const controller = new InMemoryHandlersController([])
    const httpHandler = http.get('/', () => {})
    controller.use([httpHandler])

    expect(controller.currentHandlers()).toEqual([httpHandler])
    expect(controller.getHandlersByKind('request')).toEqual([httpHandler])
  })

  test('prepends a single handler', () => {
    const httpOne = http.get('/', () => {})
    const httpTwo = http.get('/', () => {})

    const controller = new InMemoryHandlersController([httpOne])
    controller.use([httpTwo])

    expect(controller.currentHandlers()).toEqual([httpTwo, httpOne])
    expect(controller.getHandlersByKind('request')).toEqual([httpTwo, httpOne])
  })

  test('prepends multiple handlers', () => {
    const httpOne = http.get('/', () => {})
    const httpTwo = http.get('/', () => {})
    const httpThree = http.get('/', () => {})

    const controller = new InMemoryHandlersController([httpOne])

    controller.use([httpTwo, httpThree])

    expect(controller.currentHandlers()).toEqual([httpTwo, httpThree, httpOne])
    expect(controller.getHandlersByKind('request')).toEqual([
      httpTwo,
      httpThree,
      httpOne,
    ])
  })

  test('preserves order of handlers', () => {
    const httpOne = http.get('/', () => {})
    const graphqlOne = gql.query('', () => {})
    const httpTwo = http.get('/', () => {})

    const controller = new InMemoryHandlersController([httpOne])
    controller.use([graphqlOne, httpTwo])

    expect(controller.currentHandlers()).toEqual([graphqlOne, httpTwo, httpOne])
  })

  test('propagates siblings to their kind buckets at runtime', () => {
    const controller = new InMemoryHandlersController([])
    const wsHandler = ws.link('*').addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsHandler)

    controller.use([wsHandler])

    expect(controller.getHandlersByKind('websocket')).toEqual([wsHandler])
    expect(controller.getHandlersByKind('request')).toEqual([upgradeHandler])
  })

  test('prepends incoming siblings before existing handlers of the same kind', () => {
    const existingHttp = http.get('/existing', () => {})
    const controller = new InMemoryHandlersController([existingHttp])
    const wsHandler = ws.link('*').addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsHandler)

    controller.use([wsHandler])

    expect(controller.getHandlersByKind('request')).toEqual([
      upgradeHandler,
      existingHttp,
    ])
  })

  test('dedupes the shared upgrade sibling when called with multiple handlers from the same link', () => {
    const chat = ws.link('*')
    const wsOne = chat.addEventListener('connection', () => {})
    const wsTwo = chat.addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsOne)

    const controller = new InMemoryHandlersController([])
    controller.use([wsOne, wsTwo])

    expect(controller.getHandlersByKind('websocket')).toEqual([wsOne, wsTwo])
    expect(controller.getHandlersByKind('request')).toEqual([upgradeHandler])
  })

  test('dedupes the shared upgrade sibling against already-registered handlers', () => {
    const chat = ws.link('*')
    const wsOne = chat.addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsOne)
    const controller = new InMemoryHandlersController([wsOne])

    const wsTwo = chat.addEventListener('connection', () => {})
    controller.use([wsTwo])

    expect(controller.getHandlersByKind('websocket')).toEqual([wsTwo, wsOne])
    expect(controller.getHandlersByKind('request')).toEqual([upgradeHandler])
  })

  test('moves an already-registered handler to the front when used again', () => {
    const httpOne = http.get('/one', () => {})
    const httpTwo = http.get('/two', () => {})
    const controller = new InMemoryHandlersController([httpOne, httpTwo])

    controller.use([httpTwo])

    expect(controller.getHandlersByKind('request')).toEqual([httpTwo, httpOne])
  })
})

describe(InMemoryHandlersController.prototype.reset, () => {
  test('resets to the initial handlers if called with an empty list', () => {
    {
      const controller = new InMemoryHandlersController([])
      controller.reset([])
      expect(controller.currentHandlers()).toEqual([])
    }

    {
      const httpHandler = http.get('/', () => {})
      const controller = new InMemoryHandlersController([httpHandler])

      controller.reset([])
      expect(controller.currentHandlers()).toEqual([httpHandler])
    }
  })

  test('replaces the initial handlers if called with a list of handlers', () => {
    const httpOne = http.get('/', () => {})
    const httpTwo = http.get('/', () => {})
    const controller = new InMemoryHandlersController([httpOne])

    controller.reset([httpTwo])
    expect(controller.currentHandlers()).toEqual([httpTwo])
  })

  test('resets the initial handlers after runtime handlers are applied', () => {
    const httpOne = http.get('/', () => {})
    const httpTwo = http.get('/', () => {})
    const controller = new InMemoryHandlersController([])
    controller.use([httpOne])

    controller.reset([httpTwo])
    expect(controller.currentHandlers()).toEqual([httpTwo])

    controller.reset([])
    /**
     * @note There's no way to "clear" the initial state via ".reset()".
     * You can only provide the next initial state. The public-facing ".resetHandlers()"
     * spread the arguments so there's no distinction between () and ([]).
     */
    expect(controller.currentHandlers()).toEqual([httpTwo])
  })

  test('places siblings into their kind buckets when resetting to next handlers', () => {
    const controller = new InMemoryHandlersController([])
    const wsHandler = ws.link('*').addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsHandler)

    controller.reset([wsHandler])

    expect(controller.getHandlersByKind('websocket')).toEqual([wsHandler])
    expect(controller.getHandlersByKind('request')).toEqual([upgradeHandler])
  })

  test('restores siblings when resetting to the initial handlers', () => {
    const wsHandler = ws.link('*').addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsHandler)
    const controller = new InMemoryHandlersController([wsHandler])

    controller.use([http.get('/runtime', () => {})])
    controller.reset([])

    expect(controller.getHandlersByKind('websocket')).toEqual([wsHandler])
    expect(controller.getHandlersByKind('request')).toEqual([upgradeHandler])
  })

  test('dedupes the shared upgrade sibling when reset with multiple handlers from the same link', () => {
    const chat = ws.link('*')
    const wsOne = chat.addEventListener('connection', () => {})
    const wsTwo = chat.addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsOne)

    const controller = new InMemoryHandlersController([])
    controller.reset([wsOne, wsTwo])

    expect(controller.getHandlersByKind('websocket')).toEqual([wsOne, wsTwo])
    expect(controller.getHandlersByKind('request')).toEqual([upgradeHandler])
  })
})

describe(InMemoryHandlersController.prototype.listHandlers, () => {
  test('lists explicitly registered handlers, hiding their siblings', () => {
    const httpHandler = http.get('/', () => {})
    const wsHandler = ws.link('*').addEventListener('connection', () => {})

    const controller = new InMemoryHandlersController([httpHandler, wsHandler])

    expect(controller.listHandlers()).toEqual([httpHandler, wsHandler])
  })

  test('hides siblings of runtime handlers', () => {
    const controller = new InMemoryHandlersController([])
    const wsHandler = ws.link('*').addEventListener('connection', () => {})

    controller.use([wsHandler])

    expect(controller.listHandlers()).toEqual([wsHandler])
  })

  test('keeps siblings in "currentHandlers()" so the handler lifecycle reaches them', () => {
    const wsHandler = ws.link('*').addEventListener('connection', () => {})
    const [upgradeHandler] = getSiblingHandlers(wsHandler)

    const controller = new InMemoryHandlersController([wsHandler])

    expect(controller.currentHandlers()).toEqual([wsHandler, upgradeHandler])
  })
})

describe(InMemoryHandlersController.prototype.getHandlersByKind, () => {
  test('returns an empty array given an empty controller', () => {
    const controller = new InMemoryHandlersController([])
    expect(controller.getHandlersByKind('request')).toEqual([])
  })

  test('returns an empty array given no handlers by the given kind', () => {
    expect(
      new InMemoryHandlersController([
        http.get('/', () => {}),
        gql.query('', () => {}),
      ]).getHandlersByKind('websocket'),
    ).toEqual([])

    const wsHandler = ws.link('*').addEventListener('connection', () => {})
    expect(
      new InMemoryHandlersController([wsHandler]).getHandlersByKind('request'),
    ).toEqual(getSiblingHandlers(wsHandler))
  })

  test('returns all handlers if they all match', () => {
    const httpHandler = http.get('/', () => {})
    const graphqlHandler = gql.query('', () => {})
    const wsHandler = ws.link('*').addEventListener('connection', () => {})

    expect(
      new InMemoryHandlersController([
        httpHandler,
        graphqlHandler,
      ]).getHandlersByKind('request'),
    ).toEqual([httpHandler, graphqlHandler])

    expect(
      new InMemoryHandlersController([wsHandler]).getHandlersByKind(
        'websocket',
      ),
    ).toEqual([wsHandler])
  })

  test('returns only the matching handlers', () => {
    const httpHandler = http.get('/', () => {})
    const graphqlHandler = gql.query('', () => {})
    const wsHandler = ws.link('*').addEventListener('connection', () => {})
    const wsHandlerSiblings = getSiblingHandlers(wsHandler)

    expect(
      new InMemoryHandlersController([
        httpHandler,
        graphqlHandler,
        wsHandler,
      ]).getHandlersByKind('request'),
    ).toEqual([httpHandler, graphqlHandler, ...wsHandlerSiblings])

    expect(
      new InMemoryHandlersController([
        httpHandler,
        graphqlHandler,
        wsHandler,
      ]).getHandlersByKind('websocket'),
    ).toEqual([wsHandler])
  })

  test('preserves the order of returned handlers', () => {
    const httpOne = http.get('/', () => {})
    const httpTwo = http.get('/', () => {})
    const httpThree = http.get('/', () => {})

    expect(
      new InMemoryHandlersController([
        httpOne,
        httpTwo,
        httpThree,
      ]).getHandlersByKind('request'),
    ).toEqual([httpOne, httpTwo, httpThree])

    const graphqlOne = gql.query('', () => {})
    const graphqlTwo = gql.query('', () => {})
    const graphqlThree = gql.query('', () => {})

    expect(
      new InMemoryHandlersController([
        graphqlOne,
        graphqlTwo,
        graphqlThree,
      ]).getHandlersByKind('request'),
    ).toEqual([graphqlOne, graphqlTwo, graphqlThree])

    const wsOne = ws.link('*').addEventListener('connection', () => {})
    const wsTwo = ws.link('*').addEventListener('connection', () => {})
    const wsThree = ws.link('*').addEventListener('connection', () => {})

    expect(
      new InMemoryHandlersController([wsOne, wsTwo, wsThree]).getHandlersByKind(
        'websocket',
      ),
    ).toEqual([wsOne, wsTwo, wsThree])
  })
})