assertDateBefore

Assert that a Date holds an earlier instant than the expected one, with type-narrowing.

Comparing two instants through assertLessThan means reading epoch milliseconds out of the failure.

This reports both Dates in ISO form.

Usage

import { assertDateBefore } from "@kensio/smartass";

const createdAt: unknown = new Date("2026-01-01T00:00:00.000Z");

assertDateBefore(createdAt, new Date("2026-06-01T00:00:00.000Z"));

// createdAt is now narrowed to Date

Source

Source file: src/assert/date-before/date-before.assert.ts