chore: eliminate all test warnings (2538 → 0)

- Fix createPlugin inject to suppress Vue warning when fallback exists
- Add hasInjectionContext guard to useForm
- Fix PopoverRoot non-namespaced context key
- Namespace all test context keys with test: or v0: prefix
- Wrap effectScope for composables using onScopeDispose
- Assert expected warnings instead of silently swallowing
- Update testing rules with zero-warnings policy

Author: johnleider

.claude/rules/testing.md

@@ -22,7 +22,7 @@ import { mount } from '@vue/test-utils'
 // Mock Vue DI when needed
 vi.mock('vue', async () => {
   const actual = await vi.importActual('vue')
-  return { ...actual, provide: vi.fn(), inject: vi.fn() }
+  return { ...actual, provide: vi.fn(), inject: vi.fn(), hasInjectionContext: vi.fn(() => true) }
 })
 
 describe('composableName', () => {
@@ -80,6 +80,72 @@ describe('createFoo', () => {
 
 For lifecycle-dependent composables, wrap in `effectScope()`.
 
+## Zero Warnings Policy
+
+Tests must produce **zero** `stderr` output. Run `npx vitest run --reporter verbose 2>&1 | grep -E '\[Vue warn\]|\[v0.*warn\]|\[v0:context\]'` to verify.
+
+### Namespace keys
+
+All string keys passed to `createContext()` or `createXContext({ namespace })` must contain `:`.
+Use `test:` prefix for test-only keys, `v0:` for production keys.
+
+```ts
+// wrong — triggers [v0:context] namespace warning
+createContext('my-key')
+createFooContext({ namespace: 'custom' })
+
+// right
+createContext('test:my-key')
+createFooContext({ namespace: 'test:custom' })
+```
+
+### Composables that use `onScopeDispose`
+
+If a composable calls `onScopeDispose` internally (e.g. `createCombobox`, `useVirtualFocus`), wrap calls in `effectScope()`:
+
+```ts
+let scope: EffectScope
+
+function setup(options = {}) {
+  let ctx: ReturnType<typeof createCombobox>
+  scope = effectScope()
+  scope.run(() => { ctx = createCombobox(options) })
+  return ctx!
+}
+
+afterEach(() => { scope?.stop() })
+```
+
+### Expected warnings
+
+When a test intentionally triggers a warning (error paths, duplicate registration, etc.), capture it with `vi.spyOn` and **assert** it was called — never silently swallow:
+
+```ts
+const spy = vi.spyOn(console, 'warn').mockImplementation(() => {})
+
+// ... code that warns ...
+
+expect(spy).toHaveBeenCalledTimes(1)
+expect(spy).toHaveBeenCalledWith(expect.stringContaining('expected message'))
+spy.mockRestore()
+```
+
+### Vue DI mocks
+
+When mocking `provide`/`inject` from Vue and the composable under test uses `hasInjectionContext()`, include it in the mock:
+
+```ts
+vi.mock('vue', async () => {
+  const actual = await vi.importActual('vue')
+  return {
+    ...actual,
+    provide: vi.fn(),
+    inject: vi.fn(),
+    hasInjectionContext: vi.fn(() => true),
+  }
+})
+```
+
 ## Component Test Pattern
 
 ```ts

packages/0/src/components/AlertDialog/index.test.ts

@@ -802,6 +802,8 @@ describe('alert-dialog', () => {
     })
 
     it('should support async confirm flow', async () => {
+      const spy = vi.spyOn(console, 'warn').mockImplementation(() => {})
+
       const isOpen = ref(true)
       let closeFn: (() => void) | undefined
 
@@ -855,6 +857,9 @@ describe('alert-dialog', () => {
       await nextTick()
 
       expect(isOpen.value).toBe(false)
+      expect(spy).toHaveBeenCalledTimes(1)
+
+      spy.mockRestore()
     })
   })
 })

packages/0/src/components/Button/index.test.ts

@@ -658,13 +658,18 @@ describe('button', () => {
     })
 
     it('should serialize object values to JSON', () => {
+      const spy = vi.spyOn(console, 'warn').mockImplementation(() => {})
+
       const wrapper = mount(Button.Root, {
         slots: {
           default: () => h(Button.HiddenInput as any, { name: 'data', value: { foo: 'bar' } }),
         },
       })
 
       expect(wrapper.find('input').attributes('value')).toBe('{"foo":"bar"}')
+      expect(spy).toHaveBeenCalledTimes(1)
+
+      spy.mockRestore()
     })
   })
 })

packages/0/src/components/Popover/PopoverRoot.vue

@@ -37,7 +37,7 @@
     toggle: () => void
   }
 
-  export const [usePopoverContext, providePopoverContext] = createContext<PopoverContext>('Popover')
+  export const [usePopoverContext, providePopoverContext] = createContext<PopoverContext>('v0:popover')
 </script>
 
 <script setup lang="ts">

packages/0/src/components/Snackbar/index.test.ts

@@ -388,6 +388,8 @@ describe('snackbar', () => {
 
   describe('integration', () => {
     it('should render Portal > Queue > Root > Content + Close', () => {
+      const spy = vi.spyOn(console, 'warn').mockImplementation(() => {})
+
       const [, provide, context] = createNotificationsContext()
       context.send({ subject: 'File uploaded', id: 'upload-1' })
 
@@ -418,6 +420,9 @@ describe('snackbar', () => {
       expect(wrapper.findComponent(Snackbar.Root as any).exists()).toBe(true)
       expect(wrapper.findComponent(Snackbar.Content as any).text()).toBe('File uploaded')
       expect(wrapper.findComponent(Snackbar.Close as any).attributes('aria-label')).toBe('Close')
+      expect(spy).toHaveBeenCalledTimes(1)
+
+      spy.mockRestore()
     })
   })
 })