Merge pull request #37 from paralleldrive/claude/update-tdd-test-utils-011CUR6ynuCB73g4t8v8htr8

docs: add Vitest/Riteway test utils tips to TDD rules

Author: ericelliott

ai/rules/tdd.mdc

@@ -55,6 +55,14 @@ Use the string in the `test` function to offer a brief category for the test, e.
 
 Because of conflicts with the `assert` function API and description, avoid the `it` wrapper entirely, if possible.
 
+## Default Test Utils
+
+For Vitest/Riteway tests:
+- Spies and stubs: vi.fn and vi.spyOn
+  - Vitest ships tinyspy under the hood. Simple, fast, and no extra deps.
+- Module mocking: vi.mock with vi.importActual for partial mocks
+  - Works cleanly with ESM. Avoid require.
+- Timers: vi.useFakeTimers and vi.setSystemTime
 
 Constraints {
   Unless directed otherwise, always colocate tests with the code they are testing.