diff --git a/libraries/deno-commons-mod.ts b/libraries/deno-commons-mod.ts
index 5a1fed1..874d973 100644
--- a/libraries/deno-commons-mod.ts
+++ b/libraries/deno-commons-mod.ts
@@ -1,8 +1,13 @@
 // Reference:
 // - https://docs.deno.com/runtime/fundamentals/testing/
 
+import { assert } from "jsr:@std/assert/assert";
 import { assertEquals } from "jsr:@std/assert";
 
+export async function sleep(timeoutMillis: number): Promise<void> {
+    await new Promise(resolve => setTimeout(resolve, timeoutMillis))
+}
+
 export function compareVersion(ver1: string, ver2: string): 0 | 1 | -1 {
     if (ver1 === ver2) return 0;
     const ver1Parts = ver1.split(".");
@@ -287,3 +292,10 @@ Deno.test("formatPercent", () => {
     assertEquals("0.00%", formatPercent(1, 100000));
     assertEquals("100.00%", formatPercent(100, 100));
 });
+
+Deno.test("sleep", async () => {
+    const t1 = new Date().getTime();
+    await sleep(1000)
+    const t2 = new Date().getTime();
+    assert(Math.abs(1000 - (t2 - t1)) < 20);
+});
\ No newline at end of file