English Русский Deutsch Español Français Bahasa Indonesia Italiano 日本語 한국어 Nederlands Português Türkçe Tiếng Việt 中文（简体）

UUID Use Case

UUID Test Data

Tests need believable, unique IDs. A batch of v4 UUIDs gives you exactly that without a database sequence.

RealisticNon-collidingv4

Version

How many

Uppercase Hyphens Braces { }

Result

Generated locally with the Web Crypto API — nothing leaves your browser.

What Is UUID Test Data?

Using UUIDs in tests mirrors production (where IDs are UUIDs) and avoids the 'id=1,2,3' anti-pattern that hides ordering bugs.
A v4 UUID batch is unique across test runs, so parallel suites do not clash.

How to generate

Generate a batch with crypto.randomUUID() in a factory.
Use them as primary and foreign keys in fixtures.
Never hardcode a specific UUID unless a test needs it.

Use Cases

Unit test factories.
Integration fixtures.
Snapshot seeds.

Code Examples

JavaScript

const makeUser = () => ({ id: crypto.randomUUID(), name: 'Test' });

Python

import uuid
user = {'id': str(uuid.uuid4()), 'name': 'Test'}

Frequently Asked Questions

Hardcode a UUID in a test?

Only when the test asserts on that exact value; otherwise generate fresh to avoid cross-test coupling.

UUIDs slow down tests?

No — generation is microseconds; the realism benefit outweighs it.

Related tools

UUID v1 Generator UUID v3 Generator UUID v4 Generator UUID v5 Generator UUID v6 Generator UUID v7 Generator UUID v8 Generator Bulk UUID Generator Short UUID Generator UUID Validator UUID Formatter UUID as a Primary Key UUID Database ID UUID Foreign Key UUID Shard Key UUID Partition Key UUID in a Composite Key UUID Surrogate Key UUID API Key UUID Session Token UUID Access Token UUID Refresh Token UUID Idempotency Key UUID Request ID UUID Correlation ID UUID Trace ID UUID CSRF Token UUID Nonce UUID Filename UUID Object Key UUID S3 Key UUID Upload ID UUID Cache Key UUID Blob Name UUID Temp File UUID User ID UUID Account ID UUID Customer ID UUID Device ID UUID Tenant ID UUID Client ID UUID Anonymous ID UUID Member ID UUID Message ID UUID Event ID UUID Job ID UUID Task ID UUID Queue Message ID UUID Transaction ID UUID Order ID UUID Invoice ID UUID Payment ID UUID Reset Token UUID Verification Token UUID Invite Code UUID API Secret UUID Share Link UUID Magic Link UUID Node ID UUID Worker ID UUID Lock ID UUID Cluster ID UUID Test Data UUID Seed Data UUID Fixture UUID Mock ID UUID Placeholder ID UUID Sample ID