import { describe, expect, it } from "vitest";
import { toIsoString } from "./date";

describe("toIsoString", () => {
  it("converts a Date to ISO string", () => {
    const d = new Date("2026-05-04T12:00:00.000Z");
    expect(toIsoString(d)).toBe("2026-05-04T12:00:00.000Z");
  });

  it("passes through an existing ISO string", () => {
    expect(toIsoString("2026-05-04T12:00:00.000Z")).toBe(
      "2026-05-04T12:00:00.000Z",
    );
  });

  it("returns null for null input", () => {
    expect(toIsoString(null)).toBeNull();
  });

  it("returns null for undefined input", () => {
    expect(toIsoString(undefined)).toBeNull();
  });
});