docs: fix & upgrade testing.ms skill for AI

AGENTS.md

@@ -10,6 +10,7 @@
 - [Git and Commit Guidelines](skills/git-and-commit-guidelines.md) – Conventional Commits format and best practices
 - [Development Notes](skills/development-notes.md) – Platform-specific notes and build time expectations
 - [Common Issues](skills/common-issues.md) – Known issues and their solutions
+- [Testing](skills/testing.md) – Running tests and test-related guidelines
 
 ## Code Style (mandatory)
 

skills/testing.md

@@ -6,3 +6,17 @@
 yarn test:unit             # Run unit tests
 yarn workspace @package-scope/package-name test:unit  # Test specific package
 ```
+
+To run single test file:
+
+```bash
+yarn workspace @package-scope/package-name test:unit --coverage=0 file.test.ts
+```
+
+### Describe
+
+If you test function, use `function.name` to reference it, to make renaming easier:
+
+```ts
+describe(calculateCircle.name, () => {}
+```