Cross-field Validation with dependsOn

Use test(...).dependsOn(...) to declare field dependencies for focused runs.

import { create, test, enforce } from 'vest';

const suite = create((data: { password: string; confirmPassword: string }) => {
  test('password', 'Password is required', () => {
    enforce(data.password).isNotEmpty();
  });

  test('confirmPassword', 'Passwords must match', () => {
    enforce(data.confirmPassword).equals(data.password);
  }).dependsOn('password');
});

What it does

dependsOn is syntactic sugar over include(field).when(depField).

// Equivalent wiring:
include('confirmPassword').when('password');

The 3 Pillars

1. Focus Sync: when a dependency is focused with suite.only(...), the dependent test is included too.
2. Dirty-Field Guard: the dependent test is included only after it has been tested at least once, so untouched fields do not light up too early.
3. Validity Link: if any dependency is invalid, the dependent field is considered invalid.

Multiple dependencies

test('total', 'Total must be 100', () => {
  enforce(Number(data.a) + Number(data.b) + Number(data.c)).equals(100);
}).dependsOn('a', 'b', 'c');

Rules and edge cases

• Self-dependency is not allowed (test('x', ...).dependsOn('x')) and throws.
• dependsOn can be combined with manual include(...).when(...) rules.
• It works in grouped tests and async tests as well.

Typed suites

When using typed methods from a typed suite, dependsOn is typed to your suite fields.

const suite = create<'USERNAME' | 'PASSWORD'>(() => {
  const { test } = suite;

  test('PASSWORD', 'Required', () => false).dependsOn('USERNAME');
  // test('PASSWORD', 'Required', () => false).dependsOn('EMAIL'); // TS error
});