123456789101112131415
const { copy, test } = Deno;import { assertEquals } from "../testing/asserts.ts";import { StringWriter } from "./writers.ts";import { StringReader } from "./readers.ts";import { copyN } from "./ioutil.ts";
test(async function ioStringWriter(): Promise<void> {  const w = new StringWriter("base");  const r = new StringReader("0123456789");  await copyN(w, r, 4);  assertEquals(w.toString(), "base0123");  await copy(w, r);  assertEquals(w.toString(), "base0123456789");});