chore: migrate tests from tests-ui/ to colocate with source files (#7811)

## Summary

Migrates all unit tests from `tests-ui/` to colocate with their source
files in `src/`, improving discoverability and maintainability.

## Changes

- **What**: Relocated all unit tests to be adjacent to the code they
test, following the `<source>.test.ts` naming convention
- **Config**: Updated `vitest.config.ts` to remove `tests-ui` include
pattern and `@tests-ui` alias
- **Docs**: Moved testing documentation to `docs/testing/` with updated
paths and patterns

## Review Focus

- Migration patterns documented in
`temp/plans/migrate-tests-ui-to-src.md`
- Tests use `@/` path aliases instead of relative imports
- Shared fixtures placed in `__fixtures__/` directories

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7811-chore-migrate-tests-from-tests-ui-to-colocate-with-source-files-2da6d73d36508147a4cce85365dee614)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: GitHub Action <action@github.com>

src/platform/cloud/subscription/composables/useSubscriptionCredits.test.ts

@@ -0,0 +1,161 @@
+import { createPinia, setActivePinia } from 'pinia'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import type * as VueI18nModule from 'vue-i18n'
+
+import * as comfyCredits from '@/base/credits/comfyCredits'
+import { useSubscriptionCredits } from '@/platform/cloud/subscription/composables/useSubscriptionCredits'
+import { useFirebaseAuthStore } from '@/stores/firebaseAuthStore'
+import type { operations } from '@/types/comfyRegistryTypes'
+
+type GetCustomerBalanceResponse =
+  operations['GetCustomerBalance']['responses']['200']['content']['application/json']
+
+vi.mock(
+  'vue-i18n',
+  async (importOriginal: () => Promise<typeof VueI18nModule>) => {
+    const actual = await importOriginal()
+    return {
+      ...actual,
+      useI18n: () => ({
+        t: () => 'Credits',
+        locale: { value: 'en-US' }
+      })
+    }
+  }
+)
+
+// Mock Firebase Auth and related modules
+vi.mock('vuefire', () => ({
+  useFirebaseAuth: vi.fn(() => ({
+    onAuthStateChanged: vi.fn(),
+    setPersistence: vi.fn()
+  }))
+}))
+
+vi.mock('firebase/auth', () => ({
+  onAuthStateChanged: vi.fn(() => {
+    // Mock the callback to be called immediately for testing
+    return vi.fn()
+  }),
+  onIdTokenChanged: vi.fn(),
+  setPersistence: vi.fn().mockResolvedValue(undefined),
+  browserLocalPersistence: {},
+  GoogleAuthProvider: class {
+    addScope = vi.fn()
+    setCustomParameters = vi.fn()
+  },
+  GithubAuthProvider: class {
+    addScope = vi.fn()
+    setCustomParameters = vi.fn()
+  }
+}))
+
+// Mock other dependencies
+vi.mock('@/services/dialogService', () => ({
+  useDialogService: () => ({
+    showDialog: vi.fn()
+  })
+}))
+
+vi.mock('@/platform/telemetry', () => ({
+  useTelemetry: () => ({
+    track: vi.fn()
+  })
+}))
+
+vi.mock('@/stores/toastStore', () => ({
+  useToastStore: () => ({
+    add: vi.fn()
+  })
+}))
+
+vi.mock('@/stores/apiKeyAuthStore', () => ({
+  useApiKeyAuthStore: () => ({
+    headers: {}
+  })
+}))
+
+describe('useSubscriptionCredits', () => {
+  let authStore: ReturnType<typeof useFirebaseAuthStore>
+
+  beforeEach(() => {
+    setActivePinia(createPinia())
+    authStore = useFirebaseAuthStore()
+    vi.clearAllMocks()
+  })
+
+  describe('totalCredits', () => {
+    it('should return "0" when balance is null', () => {
+      authStore.balance = null
+      const { totalCredits } = useSubscriptionCredits()
+      expect(totalCredits.value).toBe('0')
+    })
+
+    it('should return "0" when amount_micros is missing', () => {
+      authStore.balance = {} as GetCustomerBalanceResponse
+      const { totalCredits } = useSubscriptionCredits()
+      expect(totalCredits.value).toBe('0')
+    })
+
+    it('should format amount_micros correctly', () => {
+      authStore.balance = { amount_micros: 100 } as GetCustomerBalanceResponse
+      const { totalCredits } = useSubscriptionCredits()
+      expect(totalCredits.value).toBe('211')
+    })
+
+    it('should handle formatting errors by throwing', async () => {
+      const formatSpy = vi.spyOn(comfyCredits, 'formatCreditsFromCents')
+      formatSpy.mockImplementationOnce(() => {
+        throw new Error('Formatting error')
+      })
+
+      authStore.balance = { amount_micros: 100 } as GetCustomerBalanceResponse
+      const { totalCredits } = useSubscriptionCredits()
+      expect(() => totalCredits.value).toThrow('Formatting error')
+      formatSpy.mockRestore()
+    })
+  })
+
+  describe('monthlyBonusCredits', () => {
+    it('should return "0" when cloud_credit_balance_micros is missing', () => {
+      authStore.balance = {} as GetCustomerBalanceResponse
+      const { monthlyBonusCredits } = useSubscriptionCredits()
+      expect(monthlyBonusCredits.value).toBe('0')
+    })
+
+    it('should format cloud_credit_balance_micros correctly', () => {
+      authStore.balance = {
+        cloud_credit_balance_micros: 200
+      } as GetCustomerBalanceResponse
+      const { monthlyBonusCredits } = useSubscriptionCredits()
+      expect(monthlyBonusCredits.value).toBe('422')
+    })
+  })
+
+  describe('prepaidCredits', () => {
+    it('should return "0" when prepaid_balance_micros is missing', () => {
+      authStore.balance = {} as GetCustomerBalanceResponse
+      const { prepaidCredits } = useSubscriptionCredits()
+      expect(prepaidCredits.value).toBe('0')
+    })
+
+    it('should format prepaid_balance_micros correctly', () => {
+      authStore.balance = {
+        prepaid_balance_micros: 300
+      } as GetCustomerBalanceResponse
+      const { prepaidCredits } = useSubscriptionCredits()
+      expect(prepaidCredits.value).toBe('633')
+    })
+  })
+
+  describe('isLoadingBalance', () => {
+    it('should reflect authStore.isFetchingBalance', () => {
+      authStore.isFetchingBalance = true
+      const { isLoadingBalance } = useSubscriptionCredits()
+      expect(isLoadingBalance.value).toBe(true)
+
+      authStore.isFetchingBalance = false
+      expect(isLoadingBalance.value).toBe(false)
+    })
+  })
+})