import { test } from "node:test";
import assert from "node:assert/strict";
import { factorial } from "../src/factorial.js";

test("factorial of zero and one", () => {
  assert.strictEqual(factorial(0), 1);
  assert.strictEqual(factorial(1), 1);
});

test("factorial of positive integers", () => {
  assert.strictEqual(factorial(5), 120);
  assert.strictEqual(factorial(10), 3628800);
});

test("factorial returns undefined for invalid inputs", () => {
  assert.strictEqual(factorial(-1), undefined);
  assert.strictEqual(factorial(2.5), undefined);
  assert.strictEqual(factorial(NaN), undefined);
  assert.strictEqual(factorial(Infinity), undefined);
});