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43 lines
1.2 KiB
43 lines
1.2 KiB
1 year ago
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import { Delays, greeter } from '../src/main.js';
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describe('greeter function', () => {
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const name = 'John';
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let hello: string;
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let timeoutSpy: jest.SpyInstance;
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// Act before assertions
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beforeAll(async () => {
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// Read more about fake timers
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// http://facebook.github.io/jest/docs/en/timer-mocks.html#content
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// Jest 27 now uses "modern" implementation of fake timers
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// https://jestjs.io/blog/2021/05/25/jest-27#flipping-defaults
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// https://github.com/facebook/jest/pull/5171
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jest.useFakeTimers();
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timeoutSpy = jest.spyOn(global, 'setTimeout');
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const p: Promise<string> = greeter(name);
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jest.runOnlyPendingTimers();
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hello = await p;
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});
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// Teardown (cleanup) after assertions
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afterAll(() => {
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timeoutSpy.mockRestore();
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});
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// Assert if setTimeout was called properly
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it('delays the greeting by 2 seconds', () => {
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expect(setTimeout).toHaveBeenCalledTimes(1);
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expect(setTimeout).toHaveBeenLastCalledWith(
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expect.any(Function),
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Delays.Long,
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);
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});
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// Assert greeter result
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it('greets a user with `Hello, {name}` message', () => {
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expect(hello).toBe(`Hello, ${name}`);
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});
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});
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