Add React Testing Library UI component tests

app/api/chat/route.test.ts

@@ -0,0 +1,45 @@
+import type { UIMessage } from "ai"
+import { POST } from "./route"
+
+vi.mock("@/lib/constants", () => ({
+  CHATBOT_ENABLED: false,
+  CHATBOT_MODEL: "claude-haiku-4-5",
+  DEBUG: false,
+}))
+
+vi.mock("@/lib/retrieval", () => ({
+  retrieveContext: vi.fn().mockResolvedValue("mocked context"),
+}))
+
+function makeRequest(body: unknown): Request {
+  return new Request("http://localhost/api/chat", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(body),
+  })
+}
+
+function makeMessages(text = "hello"): UIMessage[] {
+  return [{ id: "1", role: "user", parts: [{ type: "text", text }] }]
+}
+
+describe("POST /api/chat", () => {
+  it("returns 400 when messages is an empty array", async () => {
+    const res = await POST(makeRequest({ messages: [] }))
+    expect(res.status).toBe(400)
+    expect(await res.text()).toBe("messages must be a non-empty array")
+  })
+
+  it("returns 400 when body has no messages field", async () => {
+    const res = await POST(makeRequest({}))
+    expect(res.status).toBe(400)
+    expect(await res.text()).toBe("messages must be a non-empty array")
+  })
+
+  it("returns the offline message when CHATBOT_ENABLED is false", async () => {
+    const res = await POST(makeRequest({ messages: makeMessages() }))
+    expect(res.status).toBe(200)
+    const text = await res.text()
+    expect(text).toContain("The Oracle is currently offline.")
+  })
+})

app/api/chat/route.ts

@@ -23,7 +23,11 @@ export const POST = async (req: Request) => {
     const stream = createUIMessageStream({
       execute: ({ writer }) => {
         writer.write({ type: "text-start", id })
-        writer.write({ type: "text-delta", id, delta: "The Oracle is currently offline." })
+        writer.write({
+          type: "text-delta",
+          id,
+          delta: "The Oracle is currently offline.",
+        })
         writer.write({ type: "text-end", id })
       },
     })

components/ChatInput.test.tsx

@@ -0,0 +1,69 @@
+import { render, screen } from "@testing-library/react"
+import userEvent from "@testing-library/user-event"
+import { ChatInput } from "./ChatInput"
+
+describe("ChatInput", () => {
+  it("renders a textarea and submit button", () => {
+    render(<ChatInput onSubmit={vi.fn()} />)
+    expect(screen.getByRole("textbox")).toBeInTheDocument()
+    expect(screen.getByRole("button")).toBeInTheDocument()
+  })
+
+  it("calls onSubmit with trimmed value on button click", async () => {
+    const user = userEvent.setup()
+    const onSubmit = vi.fn()
+    render(<ChatInput onSubmit={onSubmit} />)
+    await user.type(screen.getByRole("textbox"), "  hello  ")
+    await user.click(screen.getByRole("button"))
+    expect(onSubmit).toHaveBeenCalledWith("hello")
+  })
+
+  it("calls onSubmit on Enter key", async () => {
+    const user = userEvent.setup()
+    const onSubmit = vi.fn()
+    render(<ChatInput onSubmit={onSubmit} />)
+    await user.type(screen.getByRole("textbox"), "spell{Enter}")
+    expect(onSubmit).toHaveBeenCalledWith("spell")
+  })
+
+  it("does not call onSubmit on Shift+Enter", async () => {
+    const user = userEvent.setup()
+    const onSubmit = vi.fn()
+    render(<ChatInput onSubmit={onSubmit} />)
+    await user.type(screen.getByRole("textbox"), "spell")
+    await user.keyboard("{Shift>}{Enter}{/Shift}")
+    expect(onSubmit).not.toHaveBeenCalled()
+  })
+
+  it("clears the textarea after submit", async () => {
+    const user = userEvent.setup()
+    render(<ChatInput onSubmit={vi.fn()} />)
+    const textarea = screen.getByRole("textbox")
+    await user.type(textarea, "hello")
+    await user.click(screen.getByRole("button"))
+    expect(textarea).toHaveValue("")
+  })
+
+  it("does not call onSubmit when textarea is empty", async () => {
+    const user = userEvent.setup()
+    const onSubmit = vi.fn()
+    render(<ChatInput onSubmit={onSubmit} />)
+    await user.click(screen.getByRole("button"))
+    expect(onSubmit).not.toHaveBeenCalled()
+  })
+
+  it("button is disabled when textarea is empty", () => {
+    render(<ChatInput onSubmit={vi.fn()} />)
+    expect(screen.getByRole("button")).toBeDisabled()
+  })
+
+  it("textarea and button are disabled when isDisabled is true", async () => {
+    const user = userEvent.setup()
+    const onSubmit = vi.fn()
+    render(<ChatInput onSubmit={onSubmit} isDisabled />)
+    expect(screen.getByRole("textbox")).toBeDisabled()
+    expect(screen.getByRole("button")).toBeDisabled()
+    await user.type(screen.getByRole("textbox"), "test{Enter}")
+    expect(onSubmit).not.toHaveBeenCalled()
+  })
+})

components/Message.test.tsx

@@ -0,0 +1,29 @@
+import { render, screen } from "@testing-library/react"
+import { Message } from "./Message"
+
+describe("Message", () => {
+  it("shows '> You' label for user role", () => {
+    render(<Message role="user" content="Hello" />)
+    expect(screen.getByText("> You")).toBeInTheDocument()
+  })
+
+  it("shows '🧙 Oracle' label for assistant role", () => {
+    render(<Message role="assistant" content="Hello" />)
+    expect(screen.getByText("🧙 Oracle")).toBeInTheDocument()
+  })
+
+  it("renders content", () => {
+    render(<Message role="user" content="What is AC?" />)
+    expect(screen.getByText("What is AC?")).toBeInTheDocument()
+  })
+
+  it("shows streaming cursor when isStreaming is true", () => {
+    render(<Message role="assistant" content="Thinking" isStreaming />)
+    expect(screen.getByText("█")).toBeInTheDocument()
+  })
+
+  it("hides streaming cursor by default", () => {
+    render(<Message role="assistant" content="Done" />)
+    expect(screen.queryByText("█")).not.toBeInTheDocument()
+  })
+})

components/MessageList.test.tsx

@@ -0,0 +1,53 @@
+import { render, screen } from "@testing-library/react"
+import type { UIMessage } from "ai"
+import { MessageList } from "./MessageList"
+
+window.HTMLElement.prototype.scrollIntoView = vi.fn()
+
+function makeMessage(
+  role: UIMessage["role"],
+  text: string,
+  id = crypto.randomUUID()
+): UIMessage {
+  return { id, role, parts: [{ type: "text", text }] }
+}
+
+describe("MessageList", () => {
+  it("shows placeholder when there are no messages", () => {
+    render(<MessageList messages={[]} status="ready" />)
+    expect(screen.getByText(/oracle awaits/i)).toBeInTheDocument()
+  })
+
+  it("renders all messages", () => {
+    const messages = [
+      makeMessage("user", "What is THAC0?"),
+      makeMessage("assistant", "THAC0 stands for..."),
+    ]
+    render(<MessageList messages={messages} status="ready" />)
+    expect(screen.getByText("What is THAC0?")).toBeInTheDocument()
+    expect(screen.getByText("THAC0 stands for...")).toBeInTheDocument()
+  })
+
+  it("shows 'Consulting the grimoire' when status is submitted and last message is from user", () => {
+    const messages = [makeMessage("user", "Hello")]
+    render(<MessageList messages={messages} status="submitted" />)
+    expect(screen.getByText(/consulting the grimoire/i)).toBeInTheDocument()
+  })
+
+  it("does not show loading indicator when status is ready", () => {
+    const messages = [makeMessage("user", "Hello")]
+    render(<MessageList messages={messages} status="ready" />)
+    expect(
+      screen.queryByText(/consulting the grimoire/i)
+    ).not.toBeInTheDocument()
+  })
+
+  it("marks the last assistant message as streaming during streaming status", () => {
+    const messages = [
+      makeMessage("user", "Hello", "1"),
+      makeMessage("assistant", "Hi there", "2"),
+    ]
+    render(<MessageList messages={messages} status="streaming" />)
+    expect(screen.getByText("█")).toBeInTheDocument()
+  })
+})

components/ThemeToggle.test.tsx

@@ -0,0 +1,45 @@
+import { cleanup, render, screen, waitFor } from "@testing-library/react"
+import userEvent from "@testing-library/user-event"
+import { ThemeToggle } from "./ThemeToggle"
+
+describe("ThemeToggle", () => {
+  afterEach(() => {
+    cleanup() // unmount before touching the DOM to avoid MutationObserver act() warnings
+    document.documentElement.classList.remove("dark")
+    localStorage.clear()
+  })
+
+  it("shows 'Dark' button when dark mode is off", () => {
+    render(<ThemeToggle />)
+    expect(
+      screen.getByRole("button", { name: /toggle theme/i })
+    ).toHaveTextContent("◑ Dark")
+  })
+
+  it("shows 'Light' button when dark mode is on", () => {
+    document.documentElement.classList.add("dark")
+    render(<ThemeToggle />)
+    expect(
+      screen.getByRole("button", { name: /toggle theme/i })
+    ).toHaveTextContent("◑ Light")
+  })
+
+  it("enables dark mode and saves to localStorage on click", async () => {
+    const user = userEvent.setup()
+    render(<ThemeToggle />)
+    await user.click(screen.getByRole("button", { name: /toggle theme/i }))
+    expect(document.documentElement.classList.contains("dark")).toBe(true)
+    expect(localStorage.getItem("theme")).toBe("dark")
+  })
+
+  it("disables dark mode on second click", async () => {
+    const user = userEvent.setup()
+    document.documentElement.classList.add("dark")
+    render(<ThemeToggle />)
+    await user.click(screen.getByRole("button", { name: /toggle theme/i }))
+    await waitFor(() =>
+      expect(document.documentElement.classList.contains("dark")).toBe(false)
+    )
+    expect(localStorage.getItem("theme")).toBe("light")
+  })
+})

lefthook.yml

@@ -0,0 +1,6 @@
+pre-commit:
+  commands:
+    check:
+      glob: "*.{js,ts,cjs,mjs,d.cts,d.mts,jsx,tsx,json,jsonc,md}"
+      run: npx @biomejs/biome check --write --no-errors-on-unmatched --files-ignore-unknown=true --colors=off {staged_files}
+      stage_fixed: true

package.json

@@ -30,12 +30,17 @@
   "devDependencies": {
     "@biomejs/biome": "^2.4.4",
     "@tailwindcss/postcss": "^4.2.1",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
+    "@testing-library/user-event": "^14.6.1",
     "@types/cli-progress": "^3.11.6",
     "@types/node": "^20.19.35",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
     "eslint": "^9.39.3",
     "eslint-config-next": "16.1.6",
+    "jsdom": "^28.1.0",
+    "lefthook": "^2.1.2",
     "tailwindcss": "^4.2.1",
     "tsx": "^4.21.0",
     "typescript": "^5.9.3",