deno-bootstrap/test/test.ts

import { assert, assertEquals } from "testing/asserts.ts";

Deno.test("are we operational?", async () => {
  const cmd = new Deno.Command(Deno.execPath(), {args: ["task", "dev"]});

  const { success, stdout, stderr } = await cmd.output();
  const errors = new TextDecoder().decode(stderr).split("\n");
  errors.shift();
  const output = new TextDecoder().decode(stdout).trim();

  assert(success, "success");
  assertEquals(errors.join("\n"), "", "no error output");
  assertEquals(output, "hello world!", "correct stdout");
});