test(FN-4514): complete Step 4 — add quick chat autosize regression tests

Fusion-Task-Id: FN-4514
Fusion-Task-Lineage: 5910815a-9d67-4312-97d4-44d65d01dbc7

packages/dashboard/app/components/__tests__/QuickChatFAB.autosize.test.tsx

@@ -0,0 +1,120 @@
+import { readFileSync } from "node:fs";
+import { resolve } from "node:path";
+import { describe, expect, it, vi } from "vitest";
+import { fireEvent, render, screen } from "@testing-library/react";
+import { QuickChatFAB, clampQuickChatInputHeight } from "../QuickChatFAB";
+
+vi.mock("../../api", () => ({
+  fetchDiscoveredSkills: vi.fn().mockResolvedValue([]),
+  fetchModels: vi.fn().mockResolvedValue({
+    models: [],
+    favoriteProviders: [],
+    favoriteModels: [],
+    defaultProvider: "",
+    defaultModelId: "",
+  }),
+}));
+
+vi.mock("../../hooks/useQuickChat", () => ({
+  FN_AGENT_ID: "__fn_agent__",
+  useQuickChat: vi.fn(() => ({
+    activeSession: { id: "session-1", agentId: "agent-1", modelProvider: null, modelId: null },
+    messages: [],
+    isStreaming: false,
+    streamingText: "",
+    streamingThinking: null,
+    streamingToolCalls: [],
+    sessions: [],
+    sessionsLoading: false,
+    messagesLoading: false,
+    sendMessage: vi.fn(),
+    stopStreaming: vi.fn(),
+    pendingMessage: "",
+    clearPendingMessage: vi.fn(),
+    switchSession: vi.fn(),
+    selectSession: vi.fn(),
+    startModelChat: vi.fn(),
+    startFreshSession: vi.fn(),
+    refreshSessions: vi.fn(),
+    skipNextSessionInitRef: { current: false },
+  })),
+}));
+
+vi.mock("../../hooks/useAgents", () => ({
+  useAgents: vi.fn(() => ({
+    agents: [{ id: "agent-1", name: "Agent One", role: "executor", state: "active" }],
+    activeAgents: [{ id: "agent-1", name: "Agent One", role: "executor", state: "active" }],
+    stats: null,
+    isLoading: false,
+    loadAgents: vi.fn(),
+    loadStats: vi.fn(),
+  })),
+}));
+
+vi.mock("../../hooks/useFileMention", () => ({
+  useFileMention: vi.fn(() => ({
+    mentionActive: false,
+    files: [],
+    selectedIndex: 0,
+    detectMention: vi.fn(),
+    dismissMention: vi.fn(),
+    handleKeyDown: vi.fn(),
+    selectFile: vi.fn((file: { path?: string }, text: string) => `${text}${file.path ?? ""}`),
+    selectHighlighted: vi.fn(),
+    closeMention: vi.fn(),
+    openMention: vi.fn(),
+    hasResults: false,
+    isLoading: false,
+    query: "",
+  })),
+}));
+
+vi.mock("../../hooks/useMobileKeyboard", () => ({
+  useMobileKeyboard: vi.fn(() => ({
+    keyboardOverlap: 0,
+    viewportHeight: null,
+    viewportOffsetTop: 0,
+    keyboardOpen: false,
+  })),
+}));
+
+vi.mock("../../hooks/useViewportMode", () => ({
+  useViewportMode: vi.fn(() => "desktop"),
+}));
+
+vi.mock("react-markdown", () => ({
+  default: ({ children }: { children: string }) => children,
+}));
+
+const quickChatCss = readFileSync(resolve(__dirname, "../QuickChatFAB.css"), "utf8");
+
+describe("QuickChatFAB autosize", () => {
+  it("keeps textarea CSS min/max height aligned with autosize contract", () => {
+    const textareaRule = quickChatCss.match(/\.quick-chat-textarea\s*\{[^}]*\}/);
+
+    expect(textareaRule).not.toBeNull();
+    expect(textareaRule?.[0]).toContain("max-height: 320px");
+    expect(textareaRule?.[0]).toContain("min-height: 40px");
+  });
+
+  it("clamps composer heights to the expected floor and cap", () => {
+    expect(clampQuickChatInputHeight(600)).toBe(320);
+    expect(clampQuickChatInputHeight(80)).toBe(80);
+    expect(clampQuickChatInputHeight(20)).toBe(40);
+  });
+
+  it("renders quick chat input as textarea and assigns a px height while typing", () => {
+    render(<QuickChatFAB addToast={vi.fn()} projectId="proj-1" open />);
+
+    const input = screen.getByTestId("quick-chat-input");
+    Object.defineProperty(input, "scrollHeight", {
+      configurable: true,
+      get: () => 96,
+    });
+
+    fireEvent.change(input, { target: { value: "line 1\nline 2" } });
+
+    expect(input.tagName).toBe("TEXTAREA");
+    expect((input as HTMLTextAreaElement).style.height).toMatch(/^\d+px$/);
+  });
+});