Use .toHaveReturned that the mock object successfully returned at least one time

import { expect, fn, test } from "https://deno.land/x/unitest@$VERSION/mod.ts";

test("passes when mock object returned at least once", () => {
  const mockObject = fn(() => true);
  expect(mockObject).not.toHaveReturned();
  mockObject();
  expect(mockObject).toHaveReturned();
});