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feat(waitFor): add complete and transparent support for fake timers
Closes #661
1 parent 260e1e8 commit abbfdbd

10 files changed

+166
-445
lines changed

‎src/__tests__/__snapshots__/wait-for-dom-change.js.snap

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This file was deleted.

‎src/__tests__/deprecation-warnings.js

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import {waitForElement, waitForDomChange, wait} from '..'
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afterEach(() => {
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console.warn.mockClear()
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})
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test('deprecation warnings only warn once', async () => {
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await wait(() => {}, {timeout: 1})
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await waitForElement(() => {}, {timeout: 1}).catch(e => e)
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await waitForDomChange({timeout: 1}).catch(e => e)
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expect(console.warn.mock.calls).toMatchInlineSnapshot(`
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Array [
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Array [
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"\`wait\` has been deprecated and replaced by \`waitFor\` instead. In most cases you should be able to find/replace \`wait\` with \`waitFor\`. Learn more: https://testing-library.com/docs/dom-testing-library/api-async#waitfor.",
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],
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Array [
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"\`waitForElement\` has been deprecated. Use a \`find*\` query (preferred: https://testing-library.com/docs/dom-testing-library/api-queries#findby) or use \`waitFor\` instead: https://testing-library.com/docs/dom-testing-library/api-async#waitfor",
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],
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Array [
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"\`waitForDomChange\` has been deprecated. Use \`waitFor\` instead: https://testing-library.com/docs/dom-testing-library/api-async#waitfor.",
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],
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]
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`)
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console.warn.mockClear()
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await wait(() => {}, {timeout: 1})
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await waitForElement(() => {}, {timeout: 1}).catch(e => e)
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await waitForDomChange({timeout: 1}).catch(e => e)
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expect(console.warn).not.toHaveBeenCalled()
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})

‎src/__tests__/example.js

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‎src/__tests__/fake-timers.js

+44-120
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import {waitFor, waitForElementToBeRemoved} from '..'
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import {render} from './helpers/test-utils'
23

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// Because we're using fake timers here and I don't want these tests to run
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// for the actual length of the test (because it's waiting for a timeout error)
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// we'll mock the setTimeout, clearTimeout, and setImmediate to be the ones
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// that jest will mock for us.
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jest.mock('../helpers', () => {
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const actualHelpers = jest.requireActual('../helpers')
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return {
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...actualHelpers,
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setTimeout,
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clearTimeout,
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setImmediate,
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}
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beforeAll(() => {
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jest.useFakeTimers()
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})
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jest.useFakeTimers()
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// Because of the way jest mocking works here's the order of things (and no, the order of the code above doesn't make a difference):
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// 1. Just mocks '../helpers' and setTimeout/clearTimeout/setImmediate are set to their "correct" values
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// 2. We tell Jest to use fake timers
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// 3. We reset the modules and we mock '../helpers' again so now setTimeout/clearTimeout/setImmediate are set to their mocked values
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// We're only doing this because want to mock those values so this test doesn't take 4501ms to run.
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jest.resetModules()
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const {
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wait,
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waitForElement,
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waitForDomChange,
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waitForElementToBeRemoved,
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} = require('../')
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33-
test('waitForElementToBeRemoved: times out after 4500ms by default', () => {
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const {container} = render(`<div></div>`)
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// there's a bug with this rule here...
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// eslint-disable-next-line jest/valid-expect
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const promise = expect(
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waitForElementToBeRemoved(() => container),
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).rejects.toThrowErrorMatchingInlineSnapshot(
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`"Timed out in waitForElementToBeRemoved."`,
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)
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jest.advanceTimersByTime(4501)
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return promise
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afterAll(() => {
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jest.useRealTimers()
4410
})
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test('wait: can time out', async () => {
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const promise = wait(() => {
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// eslint-disable-next-line no-throw-literal
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throw undefined
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})
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jest.advanceTimersByTime(4600)
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await expect(promise).rejects.toThrow(/timed out/i)
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})
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55-
test('waitForElement: can time out', async () => {
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const promise = waitForElement(() => {})
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jest.advanceTimersByTime(4600)
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await expect(promise).rejects.toThrow(/timed out/i)
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})
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async function runWaitFor() {
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const response = 'data'
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const doAsyncThing = () =>
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new Promise(r => setTimeout(() => r(response), 300))
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let result
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doAsyncThing().then(r => (result = r))
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61-
test('waitForElement: can specify our own timeout time', async () => {
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const promise = waitForElement(() => {}, {timeout: 4700})
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const handler = jest.fn()
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promise.then(handler, handler)
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// advance beyond the default
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jest.advanceTimersByTime(4600)
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// promise was neither rejected nor resolved
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expect(handler).toHaveBeenCalledTimes(0)
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await waitFor(() => expect(result).toBe(response))
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}
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70-
// advance beyond our specified timeout
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jest.advanceTimersByTime(150)
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// timed out
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await expect(promise).rejects.toThrow(/timed out/i)
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test('real timers', async () => {
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// the only difference when not using fake timers is this test will
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// have to wait the full length of the timeout
25+
await runWaitFor()
7526
})
7627

77-
test('waitForDomChange: can time out', async () => {
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const promise = waitForDomChange()
79-
jest.advanceTimersByTime(4600)
80-
await expect(promise).rejects.toThrow(/timed out/i)
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test('legacy', async () => {
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jest.useFakeTimers('legacy')
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await runWaitFor()
8131
})
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83-
test('waitForDomChange: can specify our own timeout time', async () => {
84-
const promise = waitForDomChange({timeout: 4700})
85-
const handler = jest.fn()
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promise.then(handler, handler)
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// advance beyond the default
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jest.advanceTimersByTime(4600)
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// promise was neither rejected nor resolved
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expect(handler).toHaveBeenCalledTimes(0)
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// advance beyond our specified timeout
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jest.advanceTimersByTime(150)
94-
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// timed out
96-
await expect(promise).rejects.toThrow(/timed out/i)
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test('modern', async () => {
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jest.useFakeTimers()
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await runWaitFor()
9736
})
9837

99-
test('wait: ensures the interval is greater than 0', async () => {
100-
// Arrange
101-
const spy = jest.fn()
102-
spy.mockImplementationOnce(() => {
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throw new Error('first time does not work')
104-
})
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const promise = wait(spy, {interval: 0})
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expect(spy).toHaveBeenCalledTimes(1)
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spy.mockClear()
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// Act
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// this line will throw an error if wait does not make the interval 1 instead of 0
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// which is why it does that!
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jest.advanceTimersByTime(0)
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// Assert
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expect(spy).toHaveBeenCalledTimes(0)
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spy.mockImplementationOnce(() => 'second time does work')
117-
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// Act
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jest.advanceTimersByTime(1)
120-
await promise
121-
122-
// Assert
123-
expect(spy).toHaveBeenCalledTimes(1)
38+
test('fake timer timeout', async () => {
39+
jest.useFakeTimers()
40+
await expect(
41+
waitFor(
42+
() => {
43+
throw new Error('always throws')
44+
},
45+
{timeout: 10},
46+
),
47+
).rejects.toMatchInlineSnapshot(`[Error: always throws]`)
12448
})
12549

126-
test('wait: times out if it runs out of attempts', () => {
127-
const spy = jest.fn(() => {
128-
throw new Error('example error')
129-
})
50+
test('times out after 1000ms by default', async () => {
51+
const {container} = render(`<div></div>`)
52+
const start = performance.now()
13053
// there's a bug with this rule here...
13154
// eslint-disable-next-line jest/valid-expect
132-
const promise = expect(
133-
wait(spy, {interval: 1, timeout: 3}),
134-
).rejects.toThrowErrorMatchingInlineSnapshot(`"example error"`)
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jest.advanceTimersByTime(1)
136-
jest.advanceTimersByTime(1)
137-
jest.advanceTimersByTime(1)
138-
return promise
55+
await expect(
56+
waitForElementToBeRemoved(() => container),
57+
).rejects.toThrowErrorMatchingInlineSnapshot(
58+
`"Timed out in waitForElementToBeRemoved."`,
59+
)
60+
// NOTE: this assertion ensures that even when we have fake timers, the
61+
// timeout still takes the full 1000ms
62+
expect(performance.now() - start).toBeGreaterThan(1000)
13963
})

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