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');
});