外部タグを分離 (#419) (#420)

**本番 DB のバックアップをかならずすること**

Reviewed-on: #420
Co-authored-by: miteruzo <miteruzo@naver.com>

frontend/src/pages/posts/PostHistoryPage.test.tsx

@@ -0,0 +1,63 @@
+import { screen, waitFor } from '@testing-library/react'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+import PostHistoryPage from '@/pages/posts/PostHistoryPage'
+import { buildTag } from '@/test/factories'
+import { renderWithProviders } from '@/test/render'
+
+const postsApi = vi.hoisted (() => ({
+  fetchPostChanges: vi.fn (),
+  updatePost:       vi.fn (),
+}))
+
+const tagsApi = vi.hoisted (() => ({
+  fetchTag:         vi.fn (),
+  fetchExternalTag: vi.fn (),
+}))
+
+vi.mock ('@/lib/posts', () => postsApi)
+vi.mock ('@/lib/tags', () => tagsApi)
+
+describe ('PostHistoryPage', () => {
+  beforeEach (() => {
+    vi.clearAllMocks ()
+
+    postsApi.fetchPostChanges.mockResolvedValue ({
+      versions: [],
+      count:    0,
+    })
+  })
+
+  it ('shows the external tag name when filtering by external_tag', async () => {
+    const external = buildTag ({
+      id:       7,
+      name:     'nico:external_history',
+      category: 'nico',
+    })
+
+    tagsApi.fetchExternalTag.mockResolvedValue (external)
+
+    renderWithProviders (
+        <PostHistoryPage/>,
+        { route: '/posts/changes?external_tag=7' },
+    )
+
+    await waitFor (() => {
+      expect (postsApi.fetchPostChanges).toHaveBeenCalledWith ({
+        externalTag: '7',
+        page:        1,
+        limit:       20,
+      })
+    })
+
+    expect (tagsApi.fetchExternalTag).toHaveBeenCalledWith ('7')
+    expect (tagsApi.fetchTag).not.toHaveBeenCalled ()
+
+    expect (
+        await screen.findByRole ('heading', {
+          level: 1,
+          name:  '耕作履歴（nico:external_history）',
+        }),
+    ).toBeInTheDocument ()
+  })
+})