Full test isolation

Domain tests boot only their domain — not the whole platform graph.

Nx·Domain Isolation·High·Since 2026-05-01

nx-isolation-test-isolation

Why it matters

Failure modes if this rule is ignored

Stake	If ignored
Spreads failure	Without this, rule 1 is empty words — if tests need the whole system, dependencies live in code even if invisible.
Slow CI	Domain tests boot the whole platform — CI minutes climb with every new app added.
Unclear failure	Shared test setup fails — every domain is red until someone finds the one bad import.

How to fix

nx affected:test is the default. CI runs only the tests for what changed. Each domain's tests use that domain's code only — no cross-domain setupX() helpers or unrelated mocks.

A test that needs the whole system up = red flag the architecture is wrong.

Examples

Bad

// .github/workflows/ci.yml
// - run: pnpm nx run-many --target=test --all

// apps/catalog/tests/item-creation.test.ts
import { setupWorkspace } from '../../workspace/test-helpers';
import { mockWorkflowRuntime } from '../../workspace/mocks';

test('creates an item', async () => {
  await setupWorkspace();           // why?
  mockWorkflowRuntime();            // unrelated to catalog
  const item = await createItem();
  expect(item).toBeDefined();
});

Good

// .github/workflows/ci.yml
// - run: pnpm nx affected --target=test --base=origin/main
// - run: pnpm nx affected --target=lint --base=origin/main
// - run: pnpm nx affected --target=build --base=origin/main

// apps/catalog/tests/item-creation.test.ts
import { createItem } from '../src/items';

test('creates an item', async () => {
  const item = await createItem({ name: 'My Item' });
  expect(item.id).toBeDefined();
});

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