/
tee_test.ts
80 lines (72 loc) · 1.71 KB
/
tee_test.ts
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// 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,
}]);
});