Studio Testing Strategy

How to write and structure tests for apps/studio/ . The core principle: push logic out of React components into pure utility functions, then test those functions exhaustively. Only use component tests for complex UI interactions. Use E2E tests for features shared between self-hosted and platform.

When to Apply

Reference these guidelines when:

• Writing new tests for Studio code

• Deciding which type of test to write (unit, component, E2E)

• Extracting logic from a component to make it testable

• Reviewing whether test coverage is sufficient

• Adding a new feature that needs tests

Rule Categories by Priority

Priority Category Impact Prefix

1 Logic Extraction CRITICAL testing-

2 Test Coverage CRITICAL testing-

3 Component Tests HIGH testing-

4 E2E Tests HIGH testing-

Quick Reference

1. Logic Extraction (CRITICAL)

• testing-extract-logic
• Remove logic from components into .utils.ts files as pure functions: args in, return out

2. Test Coverage (CRITICAL)

• testing-exhaustive-permutations
• Test every permutation of utility functions: happy path, malformed input, empty values, edge cases

3. Component Tests (HIGH)

• testing-component-tests-ui-only
• Only write component tests for complex UI interaction logic, not business logic

4. E2E Tests (HIGH)

• testing-e2e-shared-features
• Write E2E tests for features used in both self-hosted and platform; cover clicks AND keyboard shortcuts

Decision Tree: Which Test Type?

Is the logic a pure transformation (parse, format, validate, compute)? YES -> Extract to .utils.ts, write unit test with vitest NO -> Does the feature involve complex UI interactions? YES -> Is it used in both self-hosted and platform? YES -> Write E2E test in e2e/studio/features/ NO -> Write component test with customRender NO -> Can you extract the logic to make it pure? YES -> Do that, then unit test it NO -> Write a component test

How to Use

Read individual rule files for detailed explanations and code examples:

rules/testing-extract-logic.md rules/testing-exhaustive-permutations.md

Each rule file contains:

• Brief explanation of why it matters

• Incorrect code example with explanation

• Correct code example with explanation

• Real codebase references

Full Compiled Document

For the complete guide with all rules expanded: AGENTS.md

Codebase References

What Where

Util test examples tests/components/Grid/Grid.utils.test.ts , tests/components/Billing/TaxID.utils.test.ts , tests/components/Editor/SpreadsheetImport.utils.test.ts

Component test examples tests/features/logs/LogsFilterPopover.test.tsx , tests/components/CopyButton.test.tsx

E2E test example e2e/studio/features/filter-bar.spec.ts

E2E helpers pattern e2e/studio/utils/filter-bar-helpers.ts

Custom render tests/lib/custom-render.tsx

MSW mock setup tests/lib/msw.ts (addAPIMock )

Test README tests/README.md

Vitest config vitest.config.ts

Related skills e2e-studio-tests (running E2E), vitest (API reference), vercel-composition-patterns (component architecture)