Memoizing Tests

Vest introduces a new, top-level memo function. It allows you to cache parts of your suite execution based on dependencies, preventing unnecessary re-runs of expensive logic or async tests.

Why Memoize?

Validation suites often contain expensive operations, such as:

• Async checks: Checking if a username is taken (network request).
• Heavy computations: Validating complex data structures.

If the relevant data hasn't changed (e.g., the user is typing in the "password" field, but the "username" field hasn't changed), re-running the username check is wasteful. Memoization lets you skip these tests and reuse the previous result.

Unlike the previous test.memo which was limited to single tests, the new memo can wrap any part of your suite - single tests, multiple tests, groups, or arbitrary logic.

Usage

Import memo from vest:

import { create, test } from 'vest';
import { memo } from 'vest/memo';

const suite = create(data => {
  // cacheKey: [data.username]
  // If data.username hasn't changed since the last run,
  // this block is skipped, and previous results are restored.
  memo(() => {
    test('username', 'Username is taken', async () => {
      await checkAvailability(data.username);
    });
  }, [data.username]);
});

Memoizing Groups

You can use memo to skip entire groups of tests if their relevant data hasn't changed.

memo(() => {
  group('shipping_address', () => {
    test('street', 'Required', () => {
      /* ... */
    });
    test('city', 'Required', () => {
      /* ... */
    });
  });
}, [data.shipping_address]);

How it works

1. Vest checks the dependency array passed as the second argument.
2. If the dependencies match the previous run, the callback function is not executed.
3. Instead, Vest restores the test results (pass/fail/warn) produced by that block in the previous run.