std@0.139.0/async/tee_test.ts

Deno standard library
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tee_test.ts
// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.import { tee } from "./tee.ts";import { assertEquals } from "../testing/asserts.ts";
/** An example async generator */const gen = async function* iter() { yield 1; yield 2; yield 3;};
/** Testing utility for accumulating the values in async iterable. */async function accumulate<T>(src: AsyncIterable<T>): Promise<T[]> { const res: T[] = []; for await (const item of src) { res.push(item); } return res;}
Deno.test("async/tee - 2 branches", async () => { const iter = gen(); const [res0, res1] = tee(iter).map(accumulate); assertEquals( await Promise.all([res0, res1]), [ [1, 2, 3], [1, 2, 3], ], );});
Deno.test("async/tee - 3 branches - immediate consumption", async () => { const iter = gen(); const [res0, res1, res2] = tee(iter, 3).map(accumulate); assertEquals( await Promise.all([res0, res1, res2]), [ [1, 2, 3], [1, 2, 3], [1, 2, 3], ], );});
Deno.test("async/tee - 3 branches - delayed consumption", async () => { const iter = gen(); const iters = tee(iter, 3);
await new Promise<void>((resolve) => { setTimeout(() => resolve(), 20); });
assertEquals( await Promise.all(iters.map(accumulate)), [ [1, 2, 3], [1, 2, 3], [1, 2, 3], ], );});
Deno.test("async/tee - concurent .next calls", async () => { const [left] = tee(gen()); const l = left[Symbol.asyncIterator](); assertEquals(await Promise.all([l.next(), l.next(), l.next(), l.next()]), [{ value: 1, done: false, }, { value: 2, done: false, }, { value: 3, done: false, }, { value: undefined, done: true, }]);});