Function createMockInstance

packages/spy/src/index.ts:30–242

(options: MockInstanceOption = {})

const MOCK_CONFIGS = new WeakMap<Mock<Procedure | Constructable>, MockConfig>()

export function createMockInstance(options: MockInstanceOption = {}): Mock<Procedure | Constructable> {
  const {
    originalImplementation,
    restore,
    mockImplementation,
    resetToMockImplementation,
    resetToMockName,
  } = options

  if (restore) {
    MOCK_RESTORE.add(restore)
  }

  const config = getDefaultConfig(originalImplementation)
  const state = getDefaultState()

  const mock = createMock({
    config,
    state,
    ...options,
  })
  const mockLength = (mockImplementation || originalImplementation)?.length ?? 0
  Object.defineProperty(mock, 'length', {
    writable: true,
    enumerable: false,
    value: mockLength,
    configurable: true,
  })
  // inherit the default name so it appears in snapshots and logs
  // this is used by `vi.spyOn()` for better debugging.
  // when `vi.fn()` is called, we just use the default string
  if (resetToMockName) {
    config.mockName = mock.name || 'vi.fn()'
  }
  MOCK_CONFIGS.set(mock, config)
  REGISTERED_MOCKS.add(mock)

  mock._isMockFunction = true
  mock.getMockImplementation = () => {
    // Jest only returns `config.mockImplementation` here,
    // but we think it makes sense to return what the next function will be called
    return config.onceMockImplementations[0] || config.mockImplementation
  }

  Object.defineProperty(mock, 'mock', {
    configurable: false,
    enumerable: true,
    writable: false,
    value: state,
  })

  mock.mockImplementation = function mockImplementation(implementation) {
    config.mockImplementation = implementation
    return mock
  }

  mock.mockImplementationOnce = function mockImplementationOnce(implementation) {
    config.onceMockImplementations.push(implementation)