import { assertThrowsAsync } from "https://deno.land/x/cliffy@v0.11.2/packages/command/test/lib/assert.ts";
Executes a function which returns a promise, expecting it to throw or reject. If it does not, then it throws. An error class and a string that should be included in the error message can also be asserted.
Parameters
fn: () => Promise<T>