Cross-stack selector and test-id policy for web and mobile automation. Use when writing or reviewing E2E/UI test locators, or adding data-testid/accessibility identifiers to components.
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---
name: quality-engineering-selector-stability
description: Cross-stack selector and test-id policy for web and mobile automation. Use when writing or reviewing E2E/UI test locators, or adding data-testid/accessibility identifiers to components.
metadata:
triggers:
files:
- "**/e2e/**/*.{ts,js}"
- "**/*.e2e.{ts,js}"
keywords:
- selector
- locator
- data-testid
- testID
- accessibilityIdentifier
- testTag
- stable locator
- selector drift
---
# Quality Engineering: Selector Stability
## **Priority: P0 (CRITICAL)**
## Web Ladder
`getByRole` / `getByLabel` > `getByTestId` (`data-testid`) > attribute CSS. Never XPath, `nth-child`, or generated class names.
## Mobile Ladder
Accessibility id > resource-id / `testTag` > predicate/uiautomator > XPath. Never XPath.
## Framework Map
- React/Next.js: `data-testid`. React Native: `testID` + `accessibilityLabel`.
- Flutter: `Semantics(identifier:)` for black-box E2E; `WidgetKeys` stay for widget tests.
- SwiftUI/UIKit: `.accessibilityIdentifier`. Compose: `Modifier.testTag` + `testTagsAsResourceId = true`.
## Naming
`<screen>-<element>-<role>`, kebab-case (e.g. `checkout-submit-button`).
## Insertion Policy
Add ids to leaf interactive/assertable elements only, never layout wrappers. Never rename an existing id — ids are a public contract other tests depend on.
## Drift Classes
`rename` (id changed), `restructure` (DOM/tree moved), `i18n` (visible text changed, id untouched).
## Anti-Patterns
- Text selectors on translated strings, index-based locators (`nth`), generated/hashed class names.
- Using `accessibilityLabel` as a test id (it is user-facing a11y text, not a stable identifier).
- "xpath just for now" — there is no temporary XPath; use the ladder from the first commit.
## References
- [Selector Ladder Details](references/selector-ladder.md)
- [Test-ID Naming](references/testid-naming.md)
- [Insertion Policy](references/insertion-policy.md)
- [Drift Classification](references/drift-classification.md)
