test: cover post-merge gaps in utils, services, and hooks

Adds specs for the files added or modified in the recent merge that
weren't yet covered: oauthReturnPath, withATProtoImages, link,
displayLanguage, and the useGitHubContent / useImageUpload /
useNoteFreshness hooks. Locks in the new pullLatest contract
({raw, failureStatus}) and the fetchLatestSha branch semantics
(ok/unauthorized/offline).

src/hooks/useGitHubContent.hook.spec.ts

@@ -0,0 +1,197 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest"
+
+vi.mock("@/modules/repo/services/octo", () => ({
+  getOctokit: vi.fn(),
+  runWithAuthRetry: vi.fn()
+}))
+
+vi.mock("@/utils/notif", () => ({
+  confirmMessage: vi.fn(),
+  errorMessage: vi.fn()
+}))
+
+import { getOctokit, runWithAuthRetry } from "@/modules/repo/services/octo"
+import { confirmMessage, errorMessage } from "@/utils/notif"
+
+import { useGitHubContent } from "./useGitHubContent.hook"
+
+const make = () => useGitHubContent({ user: "alice", repo: "notes" })
+
+describe("useGitHubContent.fetchLatestSha", () => {
+  beforeEach(() => {
+    vi.mocked(runWithAuthRetry).mockReset()
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it("returns the sha from a file response", async () => {
+    vi.mocked(runWithAuthRetry).mockResolvedValue({
+      data: { sha: "abc123" }
+    } as never)
+
+    expect(await make().fetchLatestSha("a.md")).toEqual({
+      kind: "ok",
+      sha: "abc123"
+    })
+  })
+
+  it("returns sha=null when the path resolves to a directory (array response)", async () => {
+    vi.mocked(runWithAuthRetry).mockResolvedValue({ data: [] } as never)
+
+    expect(await make().fetchLatestSha("dir/")).toEqual({
+      kind: "ok",
+      sha: null
+    })
+  })
+
+  it("returns sha=null when the data object has no sha field", async () => {
+    vi.mocked(runWithAuthRetry).mockResolvedValue({
+      data: { type: "submodule" }
+    } as never)
+
+    expect(await make().fetchLatestSha("path")).toEqual({
+      kind: "ok",
+      sha: null
+    })
+  })
+
+  it("returns kind=unauthorized on 401", async () => {
+    vi.mocked(runWithAuthRetry).mockRejectedValue(
+      Object.assign(new Error("Unauthorized"), { status: 401 })
+    )
+
+    expect(await make().fetchLatestSha("path")).toEqual({
+      kind: "unauthorized"
+    })
+  })
+
+  it("returns kind=offline on non-401 errors (404, network, etc.)", async () => {
+    vi.mocked(runWithAuthRetry).mockRejectedValue(
+      Object.assign(new Error("Not found"), { status: 404 })
+    )
+    expect(await make().fetchLatestSha("path")).toEqual({ kind: "offline" })
+
+    vi.mocked(runWithAuthRetry).mockRejectedValue(new Error("network"))
+    expect(await make().fetchLatestSha("path")).toEqual({ kind: "offline" })
+  })
+})
+
+describe("useGitHubContent.updateFile / createFile (putFile)", () => {
+  const mockOctokitRequest = vi.fn()
+
+  beforeEach(() => {
+    mockOctokitRequest.mockReset()
+    vi.mocked(getOctokit).mockResolvedValue({
+      request: mockOctokitRequest
+    } as never)
+    vi.mocked(confirmMessage).mockReset()
+    vi.mocked(errorMessage).mockReset()
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it("returns the new sha and calls confirmMessage on success", async () => {
+    mockOctokitRequest.mockResolvedValue({
+      data: { content: { sha: "new-sha" } }
+    })
+
+    const result = await make().updateFile({
+      content: "# hello",
+      path: "a.md",
+      sha: "old-sha"
+    })
+
+    expect(result).toEqual({ sha: "new-sha", conflict: false })
+    expect(confirmMessage).toHaveBeenCalledWith("✅ Note saved")
+  })
+
+  it("flags conflict=true on 409 and 422 responses", async () => {
+    vi.spyOn(console, "warn").mockImplementation(() => {})
+
+    for (const status of [409, 422]) {
+      mockOctokitRequest.mockRejectedValueOnce(
+        Object.assign(new Error("Conflict"), { status })
+      )
+      const result = await make().createFile({ content: "x", path: "a.md" })
+      expect(result).toEqual({ sha: null, conflict: true })
+    }
+    expect(errorMessage).toHaveBeenCalledWith(
+      "⚠ Conflict: this note changed on GitHub"
+    )
+  })
+
+  it("returns conflict=false and calls errorMessage on non-conflict errors", async () => {
+    vi.spyOn(console, "warn").mockImplementation(() => {})
+    mockOctokitRequest.mockRejectedValue(
+      Object.assign(new Error("Server error"), { status: 500 })
+    )
+
+    const result = await make().updateFile({
+      content: "x",
+      path: "a.md",
+      sha: "old"
+    })
+
+    expect(result).toEqual({ sha: null, conflict: false })
+    expect(errorMessage).toHaveBeenCalledWith("❌ Note could not be saved")
+  })
+})
+
+describe("useGitHubContent.uploadBinaryFile", () => {
+  const mockOctokitRequest = vi.fn()
+
+  beforeEach(() => {
+    mockOctokitRequest.mockReset()
+    vi.mocked(getOctokit).mockResolvedValue({
+      request: mockOctokitRequest
+    } as never)
+    vi.mocked(errorMessage).mockReset()
+    vi.mocked(confirmMessage).mockReset()
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it("uploads pre-base64-encoded content without re-encoding", async () => {
+    mockOctokitRequest.mockResolvedValue({
+      data: { content: { sha: "img-sha" } }
+    })
+
+    const result = await make().uploadBinaryFile({
+      base64: "ZGF0YQ==",
+      path: "img/cover.png"
+    })
+
+    expect(result).toEqual({ sha: "img-sha", conflict: false })
+    expect(mockOctokitRequest).toHaveBeenCalledWith(
+      "PUT /repos/{owner}/{repo}/contents/{+path}",
+      expect.objectContaining({
+        path: "img/cover.png",
+        content: "ZGF0YQ=="
+      })
+    )
+    expect(confirmMessage).toHaveBeenCalledWith("✅ Image uploaded")
+  })
+
+  it("surfaces a conflict on existing file (422)", async () => {
+    vi.spyOn(console, "warn").mockImplementation(() => {})
+    mockOctokitRequest.mockRejectedValue(
+      Object.assign(new Error("Exists"), { status: 422 })
+    )
+
+    const result = await make().uploadBinaryFile({
+      base64: "Zm9v",
+      path: "img.png"
+    })
+
+    expect(result).toEqual({ sha: null, conflict: true })
+    expect(errorMessage).toHaveBeenCalledWith(
+      "⚠ A file already exists at this path on GitHub"
+    )
+  })
+})

src/hooks/useImageUpload.hook.spec.ts

@@ -0,0 +1,164 @@
+import { createPinia, setActivePinia } from "pinia"
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest"
+
+const uploadBinaryFile = vi.fn()
+const registerUploadedFile = vi.fn()
+
+vi.mock("@/hooks/useGitHubContent.hook", () => ({
+  useGitHubContent: () => ({ uploadBinaryFile })
+}))
+
+vi.mock("@/modules/repo/store/userRepo.store", () => ({
+  useUserRepoStore: () => ({
+    files: [{ path: "alice/notes/already-here.png", sha: "x" }],
+    registerUploadedFile
+  })
+}))
+
+vi.mock("@/utils/notif", () => ({
+  errorMessage: vi.fn()
+}))
+
+import { errorMessage } from "@/utils/notif"
+
+import { useImageUpload } from "./useImageUpload.hook"
+
+const makeFile = (name: string, body = "fake-image-bytes") =>
+  new File([body], name, { type: "image/png" })
+
+describe("useImageUpload", () => {
+  beforeEach(() => {
+    setActivePinia(createPinia())
+    uploadBinaryFile.mockReset()
+    registerUploadedFile.mockReset()
+    vi.mocked(errorMessage).mockReset()
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it("returns null and shows an error when notePath is missing", async () => {
+    const { uploadImage } = useImageUpload({
+      user: "alice",
+      repo: "notes",
+      notePath: undefined
+    })
+
+    expect(await uploadImage(makeFile("img.png"))).toBeNull()
+    expect(errorMessage).toHaveBeenCalledWith("❌ Image upload failed")
+    expect(uploadBinaryFile).not.toHaveBeenCalled()
+  })
+
+  it("uploads to the note's directory using the note basename and the file extension", async () => {
+    uploadBinaryFile.mockResolvedValue({ sha: "new-sha", conflict: false })
+
+    const { uploadImage } = useImageUpload({
+      user: "alice",
+      repo: "notes",
+      notePath: "alice/notes/my-note.md"
+    })
+
+    const result = await uploadImage(makeFile("photo.PNG"))
+
+    expect(result).toEqual({ filename: "my-note.png" })
+    expect(uploadBinaryFile).toHaveBeenCalledWith(
+      expect.objectContaining({
+        path: "alice/notes/my-note.png"
+      })
+    )
+  })
+
+  it("deduplicates filenames against existing files in the store", async () => {
+    uploadBinaryFile.mockResolvedValue({ sha: "new-sha", conflict: false })
+
+    const { uploadImage } = useImageUpload({
+      user: "alice",
+      repo: "notes",
+      notePath: "alice/notes/already-here.md"
+    })
+
+    const result = await uploadImage(makeFile("photo.png"))
+
+    expect(result?.filename).toBe("already-here-2.png")
+  })
+
+  it("returns null on conflict and does NOT register the file", async () => {
+    uploadBinaryFile.mockResolvedValue({ sha: null, conflict: true })
+
+    const { uploadImage } = useImageUpload({
+      user: "alice",
+      repo: "notes",
+      notePath: "x/note.md"
+    })
+
+    expect(await uploadImage(makeFile("img.png"))).toBeNull()
+    expect(registerUploadedFile).not.toHaveBeenCalled()
+  })
+
+  it("registers the uploaded file in the store on success", async () => {
+    uploadBinaryFile.mockResolvedValue({ sha: "abc", conflict: false })
+    const file = makeFile("img.png", "data")
+
+    const { uploadImage } = useImageUpload({
+      user: "alice",
+      repo: "notes",
+      notePath: "x/note.md"
+    })
+
+    await uploadImage(file)
+
+    expect(registerUploadedFile).toHaveBeenCalledWith({
+      path: "x/note.png",
+      sha: "abc",
+      type: "blob",
+      size: file.size
+    })
+  })
+
+  it("falls back to .png when the file name has no extension", async () => {
+    uploadBinaryFile.mockResolvedValue({ sha: "abc", conflict: false })
+
+    const { uploadImage } = useImageUpload({
+      user: "alice",
+      repo: "notes",
+      notePath: "x/note.md"
+    })
+
+    await uploadImage(makeFile("noextension"))
+
+    expect(uploadBinaryFile).toHaveBeenCalledWith(
+      expect.objectContaining({ path: "x/note.png" })
+    )
+  })
+
+  it("uses the root path when the note is at the repo root", async () => {
+    uploadBinaryFile.mockResolvedValue({ sha: "abc", conflict: false })
+
+    const { uploadImage } = useImageUpload({
+      user: "alice",
+      repo: "notes",
+      notePath: "root.md"
+    })
+
+    await uploadImage(makeFile("img.png"))
+
+    expect(uploadBinaryFile).toHaveBeenCalledWith(
+      expect.objectContaining({ path: "root.png" })
+    )
+  })
+
+  it("returns null and notifies on unexpected errors", async () => {
+    vi.spyOn(console, "warn").mockImplementation(() => {})
+    uploadBinaryFile.mockRejectedValue(new Error("boom"))
+
+    const { uploadImage } = useImageUpload({
+      user: "alice",
+      repo: "notes",
+      notePath: "x/note.md"
+    })
+
+    expect(await uploadImage(makeFile("img.png"))).toBeNull()
+    expect(errorMessage).toHaveBeenCalledWith("❌ Image upload failed")
+  })
+})

src/hooks/useNoteFreshness.hook.spec.ts

@@ -0,0 +1,234 @@
+import { createPinia, setActivePinia } from "pinia"
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest"
+import { ref } from "vue"
+
+const {
+  fetchLatestSha,
+  addFile,
+  getRawContent,
+  saveCacheNote,
+  queryFileContent
+} = vi.hoisted(() => ({
+  fetchLatestSha: vi.fn(),
+  addFile: vi.fn(),
+  getRawContent: vi.fn((s: string) => s),
+  saveCacheNote: vi.fn(),
+  queryFileContent: vi.fn()
+}))
+
+vi.mock("@/hooks/useGitHubContent.hook", () => ({
+  useGitHubContent: () => ({ fetchLatestSha })
+}))
+
+vi.mock("@/hooks/useMarkdown.hook", () => ({
+  markdownBuilder: () => ({ getRawContent, render: (s: string) => s })
+}))
+
+vi.mock("@/modules/note/cache/prepareNoteCache", () => ({
+  prepareNoteCache: () => ({
+    getCachedNote: async () => ({ note: null }),
+    saveCacheNote
+  })
+}))
+
+vi.mock("@/modules/repo/services/repo", () => ({
+  queryFileContent
+}))
+
+vi.mock("@/modules/repo/store/userRepo.store", () => ({
+  useUserRepoStore: () => ({ addFile })
+}))
+
+import { useNoteFreshness } from "./useNoteFreshness.hook"
+
+const setup = (overrides: { sha?: string; path?: string; edited?: string | null } = {}) => {
+  setActivePinia(createPinia())
+  const sha = ref(overrides.sha ?? "local-sha")
+  const path = ref(overrides.path ?? "note.md")
+  const getEditedSha = vi.fn().mockResolvedValue(overrides.edited ?? null)
+  return useNoteFreshness({
+    user: "alice",
+    repo: "notes",
+    sha,
+    path,
+    getEditedSha
+  })
+}
+
+// Make performance.now() return values where elapsed > MIN_SPINNER_MS so the
+// 400ms spinner-min-time wait is skipped.
+const skipSpinnerWait = () => {
+  let call = 0
+  vi.spyOn(performance, "now").mockImplementation(() =>
+    call++ === 0 ? 0 : 10_000
+  )
+}
+
+describe("useNoteFreshness.check", () => {
+  beforeEach(() => {
+    fetchLatestSha.mockReset()
+    addFile.mockReset()
+    saveCacheNote.mockReset()
+    queryFileContent.mockReset()
+    skipSpinnerWait()
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it("does nothing when path is empty", async () => {
+    const { check, status } = setup({ path: "" })
+
+    await check()
+
+    expect(status.value).toBe("unknown")
+    expect(fetchLatestSha).not.toHaveBeenCalled()
+  })
+
+  it("sets status to 'verified' when remote sha matches local sha", async () => {
+    fetchLatestSha.mockResolvedValue({ kind: "ok", sha: "local-sha" })
+
+    const { check, status, latestSha, lastCheckedAt } = setup()
+    await check()
+
+    expect(status.value).toBe("verified")
+    expect(latestSha.value).toBe("local-sha")
+    expect(lastCheckedAt.value).toBeInstanceOf(Date)
+  })
+
+  it("sets status to 'outdated' when remote sha differs from local sha", async () => {
+    fetchLatestSha.mockResolvedValue({ kind: "ok", sha: "remote-sha" })
+
+    const { check, status } = setup()
+    await check()
+
+    expect(status.value).toBe("outdated")
+  })
+
+  it("prefers the edited sha over the live sha when comparing", async () => {
+    fetchLatestSha.mockResolvedValue({ kind: "ok", sha: "edited-sha" })
+
+    const { check, status } = setup({ sha: "live-sha", edited: "edited-sha" })
+    await check()
+
+    expect(status.value).toBe("verified")
+  })
+
+  it("sets status to 'unauthorized' on auth failure", async () => {
+    fetchLatestSha.mockResolvedValue({ kind: "unauthorized" })
+
+    const { check, status } = setup()
+    await check()
+
+    expect(status.value).toBe("unauthorized")
+  })
+
+  it("sets status to 'offline' on network failure", async () => {
+    fetchLatestSha.mockResolvedValue({ kind: "offline" })
+
+    const { check, status } = setup()
+    await check()
+
+    expect(status.value).toBe("offline")
+  })
+
+  it("sets status to 'offline' when remote returns sha=null (e.g. directory)", async () => {
+    fetchLatestSha.mockResolvedValue({ kind: "ok", sha: null })
+
+    const { check, status } = setup()
+    await check()
+
+    expect(status.value).toBe("offline")
+  })
+})
+
+describe("useNoteFreshness.pullLatest", () => {
+  beforeEach(() => {
+    fetchLatestSha.mockReset()
+    addFile.mockReset()
+    saveCacheNote.mockReset()
+    queryFileContent.mockReset()
+    getRawContent.mockClear()
+    skipSpinnerWait()
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it("returns raw=null with no failureStatus when path is empty", async () => {
+    const { pullLatest } = setup({ path: "" })
+
+    expect(await pullLatest()).toEqual({ raw: null, failureStatus: null })
+    expect(fetchLatestSha).not.toHaveBeenCalled()
+  })
+
+  it("returns the fetched content and updates state on success", async () => {
+    fetchLatestSha.mockResolvedValue({ kind: "ok", sha: "remote-sha" })
+    queryFileContent.mockResolvedValue("BASE64")
+    getRawContent.mockReturnValue("# raw")
+
+    const { pullLatest, status, latestSha, lastCheckedAt } = setup()
+    const result = await pullLatest()
+
+    expect(result).toEqual({ raw: "# raw", failureStatus: null })
+    expect(status.value).toBe("verified")
+    expect(latestSha.value).toBe("remote-sha")
+    expect(lastCheckedAt.value).toBeInstanceOf(Date)
+    expect(addFile).toHaveBeenCalledWith({ path: "note.md", sha: "remote-sha" })
+    expect(saveCacheNote).toHaveBeenCalled()
+  })
+
+  it("surfaces 'unauthorized' failureStatus when remote resolve is unauthorized", async () => {
+    vi.spyOn(console, "warn").mockImplementation(() => {})
+    fetchLatestSha.mockResolvedValue({ kind: "unauthorized" })
+
+    const { pullLatest, status } = setup()
+    expect(await pullLatest()).toEqual({
+      raw: null,
+      failureStatus: "unauthorized"
+    })
+    expect(status.value).toBe("unauthorized")
+  })
+
+  it("surfaces 'offline' failureStatus when remote resolve is offline", async () => {
+    vi.spyOn(console, "warn").mockImplementation(() => {})
+    fetchLatestSha.mockResolvedValue({ kind: "offline" })
+
+    const { pullLatest, status } = setup()
+    expect(await pullLatest()).toEqual({
+      raw: null,
+      failureStatus: "offline"
+    })
+    expect(status.value).toBe("offline")
+  })
+
+  it("surfaces 'offline' failureStatus when blob content fetch fails", async () => {
+    vi.spyOn(console, "warn").mockImplementation(() => {})
+    fetchLatestSha.mockResolvedValue({ kind: "ok", sha: "remote-sha" })
+    queryFileContent.mockResolvedValue(null)
+
+    const { pullLatest, status } = setup()
+    expect(await pullLatest()).toEqual({
+      raw: null,
+      failureStatus: "offline"
+    })
+    expect(status.value).toBe("offline")
+  })
+
+  it("uses the cached latestSha to skip a redundant fetchLatestSha call", async () => {
+    fetchLatestSha.mockResolvedValueOnce({ kind: "ok", sha: "cached-sha" })
+    queryFileContent.mockResolvedValue("BASE64")
+
+    const api = setup()
+    await api.check() // populates latestSha
+    expect(fetchLatestSha).toHaveBeenCalledTimes(1)
+
+    fetchLatestSha.mockClear()
+    await api.pullLatest()
+
+    expect(fetchLatestSha).not.toHaveBeenCalled()
+    expect(queryFileContent).toHaveBeenCalledWith("alice", "notes", "cached-sha")
+  })
+})

src/modules/atproto/withATProtoImages.spec.ts

@@ -0,0 +1,55 @@
+import { describe, expect, it } from "vitest"
+
+import { withATProtoImages } from "./withATProtoImages"
+
+const PDS = "https://pds.example.com"
+const DID = "did:plc:abc123"
+
+describe("withATProtoImages", () => {
+  it("rewrites a bafkrei CID image to a getBlob URL", () => {
+    const out = withATProtoImages(
+      "![cover](bafkreigh2akiscaildc7r4apx2t6q4t6n6kxjpw3xhqxkfvvbprdaezz4i)",
+      { pds: PDS, did: DID }
+    )
+
+    expect(out).toContain(
+      `${PDS}/xrpc/com.atproto.sync.getBlob`
+    )
+    expect(out).toContain("did=did%3Aplc%3Aabc123")
+    expect(out).toContain(
+      "cid=bafkreigh2akiscaildc7r4apx2t6q4t6n6kxjpw3xhqxkfvvbprdaezz4i"
+    )
+  })
+
+  it("preserves the alt text", () => {
+    const out = withATProtoImages("![my cover](bafkreiabc)", {
+      pds: PDS,
+      did: DID
+    })
+    expect(out).toMatch(/!\[my cover\]/)
+  })
+
+  it("rewrites multiple images in one pass", () => {
+    const md = "![a](bafkreiaaa) and ![b](bafkreibbb)"
+    const out = withATProtoImages(md, { pds: PDS, did: DID })
+
+    expect(out.match(/com\.atproto\.sync\.getBlob/g)).toHaveLength(2)
+    expect(out).toContain("cid=bafkreiaaa")
+    expect(out).toContain("cid=bafkreibbb")
+  })
+
+  it("leaves regular image URLs untouched", () => {
+    const md = "![pic](https://example.com/a.png)"
+    expect(withATProtoImages(md, { pds: PDS, did: DID })).toBe(md)
+  })
+
+  it("leaves CIDs that don't match the bafkrei prefix untouched", () => {
+    const md = "![x](sha256-abc123)"
+    expect(withATProtoImages(md, { pds: PDS, did: DID })).toBe(md)
+  })
+
+  it("preserves an empty alt text", () => {
+    const out = withATProtoImages("![](bafkreiabc)", { pds: PDS, did: DID })
+    expect(out).toMatch(/^!\[\]/)
+  })
+})

src/modules/user/service/oauthReturnPath.spec.ts

@@ -0,0 +1,30 @@
+import { beforeEach, describe, expect, it } from "vitest"
+
+import {
+  consumeGithubOAuthReturnPath,
+  GITHUB_OAUTH_RETURN_PATH_KEY
+} from "./oauthReturnPath"
+
+describe("consumeGithubOAuthReturnPath", () => {
+  beforeEach(() => {
+    sessionStorage.clear()
+  })
+
+  it("returns the stored path and clears the key", () => {
+    sessionStorage.setItem(GITHUB_OAUTH_RETURN_PATH_KEY, "/alice/notes")
+
+    expect(consumeGithubOAuthReturnPath()).toBe("/alice/notes")
+    expect(sessionStorage.getItem(GITHUB_OAUTH_RETURN_PATH_KEY)).toBeNull()
+  })
+
+  it("returns null when nothing is stored", () => {
+    expect(consumeGithubOAuthReturnPath()).toBeNull()
+  })
+
+  it("returns null on the second call (consume-once semantics)", () => {
+    sessionStorage.setItem(GITHUB_OAUTH_RETURN_PATH_KEY, "/x")
+
+    expect(consumeGithubOAuthReturnPath()).toBe("/x")
+    expect(consumeGithubOAuthReturnPath()).toBeNull()
+  })
+})

src/utils/displayLanguage.spec.ts

@@ -0,0 +1,38 @@
+import { afterEach, describe, expect, it, vi } from "vitest"
+
+import { displayLanguage } from "./displayLanguage"
+
+describe("displayLanguage", () => {
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it("returns null when no language code is given", () => {
+    expect(displayLanguage()).toBeNull()
+    expect(displayLanguage("")).toBeNull()
+  })
+
+  it("returns a human-readable name for a known language code", () => {
+    expect(displayLanguage("en")).toMatch(/^English/i)
+  })
+
+  it("works for French", () => {
+    expect(displayLanguage("fr")).toBeTruthy()
+  })
+
+  it("returns null and logs a warning when Intl.DisplayNames throws", () => {
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {})
+    const original = Intl.DisplayNames
+    // Force the constructor to throw
+    ;(Intl as unknown as { DisplayNames: unknown }).DisplayNames = function () {
+      throw new Error("boom")
+    }
+
+    try {
+      expect(displayLanguage("en")).toBeNull()
+      expect(warn).toHaveBeenCalled()
+    } finally {
+      ;(Intl as unknown as { DisplayNames: unknown }).DisplayNames = original
+    }
+  })
+})

src/utils/link.spec.ts

@@ -0,0 +1,33 @@
+import { describe, expect, it } from "vitest"
+
+import { isExternalLink } from "./link"
+
+describe("isExternalLink", () => {
+  const ORIGIN = window.location.origin
+
+  it("returns false for same-origin absolute URLs", () => {
+    expect(isExternalLink(`${ORIGIN}/alice/notes`)).toBe(false)
+  })
+
+  it("returns true for an https URL on a different origin", () => {
+    expect(isExternalLink("https://github.com/anywhere")).toBe(true)
+  })
+
+  it("returns true for an http URL on a different origin", () => {
+    expect(isExternalLink("http://example.com")).toBe(true)
+  })
+
+  it("returns false for relative paths (no http/https prefix)", () => {
+    expect(isExternalLink("/alice/notes")).toBe(false)
+    expect(isExternalLink("./neighbor.md")).toBe(false)
+  })
+
+  it("returns false for mailto and other non-http schemes", () => {
+    expect(isExternalLink("mailto:user@example.com")).toBe(false)
+    expect(isExternalLink("ftp://files.example.com")).toBe(false)
+  })
+
+  it("returns false for an https URL that happens to start with the origin", () => {
+    expect(isExternalLink(`${ORIGIN}/deep/path`)).toBe(false)
+  })
+})