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refactor: add type safety in utils.test.ts #4091

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Sep 16, 2022
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refactor: add type safety in utils.test.ts #4091

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14 changes: 5 additions & 9 deletions site/src/components/GlobalSnackbar/utils.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -48,27 +48,23 @@ describe("Snackbar", () => {

describe("displaySuccess", () => {
const originalWindowDispatchEvent = window.dispatchEvent
let dispatchEventMock: jest.Mock
type TDispatchEventMock = jest.MockedFunction<(msg: CustomEvent<NotificationMsg>) => boolean>
let dispatchEventMock: TDispatchEventMock

// Helper function to extract the notification event
// that was sent to `dispatchEvent`. This lets us validate
// the contents of the notification event are what we expect.
const extractNotificationEvent = (dispatchEventMock: jest.Mock): NotificationMsg => {
// The jest mock API isn't typesafe - but we know in our usage that
// this will always be a `NotificationMsg`.

const extractNotificationEvent = (dispatchEventMock: TDispatchEventMock): NotificationMsg => {
// calls[0] is the first call made to the mock (this is reset in `beforeEach`)
// calls[0][0] is the first argument of the first call
// calls[0][0].detail is the 'detail' argument passed to the `CustomEvent` -
// this is the `NotificationMsg` object that gets sent to `dispatchEvent`

// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
return dispatchEventMock.mock.calls[0][0].detail as NotificationMsg
return dispatchEventMock.mock.calls[0][0].detail
}

beforeEach(() => {
dispatchEventMock = jest.fn()
window.dispatchEvent = dispatchEventMock
window.dispatchEvent = dispatchEventMock as unknown as typeof window.dispatchEvent
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I think this is the only way to properly type this:

  1. as unknown "Don't worry, I'm casting my thing unknown type before my assertion"
  2. as typeof window.dispatchEvent "This is what it actually is"

})

afterEach(() => {
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