cellxgene/client/__tests__/util/promiseLimit.test.js

import { PromiseLimit } from "../../src/util/promiseLimit";
import { range } from "../../src/util/range";

const delay = t => new Promise((resolve, reject) => setTimeout(resolve, t));

describe("PromiseLimit", () => {
	test("simple evaluation, concurrency 1", async () => {
		const plimit = new PromiseLimit(1);
		const result = await Promise.all([
			plimit.add(() => Promise.resolve(1)),
			plimit.add(() => Promise.resolve(2)),
			plimit.add(() => Promise.resolve(3)),
			plimit.add(() => Promise.resolve(4))
		]);
		expect(result).toEqual([1, 2, 3, 4]);
	});

	test("simple evaluation, concurrency > 1", async () => {
		const plimit = new PromiseLimit(100);
		const result = await Promise.all([
			plimit.add(() => Promise.resolve(1)),
			plimit.add(() => Promise.resolve(2)),
			plimit.add(() => Promise.resolve(3)),
			plimit.add(() => Promise.resolve(4))
		]);
		expect(result).toEqual([1, 2, 3, 4]);
	});

	test("eval in order of insertion", async () => {
		const plimit = new PromiseLimit(100);
		let counter = 0;
		const result = await Promise.all([
			plimit.add(() => Promise.resolve((counter += 1))),
			plimit.add(() => Promise.resolve((counter += 1))),
			plimit.add(() => Promise.resolve((counter += 1))),
			plimit.add(() => Promise.resolve((counter += 1)))
		]);
		expect(result).toEqual([1, 2, 3, 4]);
	});

	test("obeys concurrency limit", async () => {
		const plimit = new PromiseLimit(2);
		let running = 0;
		let maxRunning = 0;

		const cbfn = async i => {
			running = running + 1;
			maxRunning = running > maxRunning ? running : maxRunning;
			await delay(100);
			running = running - 1;
		};

		const result = await Promise.all(
			range(10).map(i => plimit.add(() => cbfn(i)))
		);
		expect(maxRunning).toEqual(2);
	});

	test("rejection", async () => {
		const plimit = new PromiseLimit(2);
		const result = await Promise.all([
			plimit.add(() => Promise.resolve("OK")),
			plimit.add(() => Promise.reject("not OK")).catch(e => e),
			plimit.add(() => Promise.resolve("OK")),
			plimit
				.add(() => {
					throw new Error("not OK");
				})
				.catch(e => e.message)
		]);
		expect(result).toEqual(["OK", "not OK", "OK", "not OK"]);
	});
});