test(15-01): add sample component test for PromptNode

- Create PromptNode.test.tsx with React Testing Library
- Test textarea rendering and placeholder
- Test initial prompt value display
- Test updateNodeData callback on user input
- Mock Zustand store and wrap with ReactFlowProvider

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/__tests__/PromptNode.test.tsx

@@ -0,0 +1,104 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import { PromptNode } from "@/components/nodes/PromptNode";
+import { ReactFlowProvider } from "@xyflow/react";
+
+// Mock the workflow store
+const mockUpdateNodeData = vi.fn();
+const mockIncrementModalCount = vi.fn();
+const mockDecrementModalCount = vi.fn();
+
+vi.mock("@/store/workflowStore", () => ({
+  useWorkflowStore: vi.fn((selector) => {
+    const state = {
+      updateNodeData: mockUpdateNodeData,
+      incrementModalCount: mockIncrementModalCount,
+      decrementModalCount: mockDecrementModalCount,
+      currentNodeId: null,
+      groups: {},
+      nodes: [],
+    };
+    return selector(state);
+  }),
+}));
+
+// Wrapper component for React Flow context
+function TestWrapper({ children }: { children: React.ReactNode }) {
+  return <ReactFlowProvider>{children}</ReactFlowProvider>;
+}
+
+describe("PromptNode", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  const defaultProps = {
+    id: "test-prompt-1",
+    type: "prompt" as const,
+    data: {
+      prompt: "",
+    },
+    selected: false,
+    isConnectable: true,
+    positionAbsoluteX: 0,
+    positionAbsoluteY: 0,
+    zIndex: 0,
+    dragging: false,
+    deletable: true,
+    selectable: true,
+    parentId: undefined,
+    dragHandle: undefined,
+  };
+
+  it("should render the textarea with placeholder", () => {
+    render(
+      <TestWrapper>
+        <PromptNode {...defaultProps} />
+      </TestWrapper>
+    );
+
+    const textarea = screen.getByPlaceholderText("Describe what to generate...");
+    expect(textarea).toBeInTheDocument();
+  });
+
+  it("should render with initial prompt value", () => {
+    const propsWithPrompt = {
+      ...defaultProps,
+      data: { prompt: "Initial prompt text" },
+    };
+
+    render(
+      <TestWrapper>
+        <PromptNode {...propsWithPrompt} />
+      </TestWrapper>
+    );
+
+    const textarea = screen.getByDisplayValue("Initial prompt text");
+    expect(textarea).toBeInTheDocument();
+  });
+
+  it("should call updateNodeData when typing in textarea", () => {
+    render(
+      <TestWrapper>
+        <PromptNode {...defaultProps} />
+      </TestWrapper>
+    );
+
+    const textarea = screen.getByPlaceholderText("Describe what to generate...");
+    fireEvent.change(textarea, { target: { value: "New prompt text" } });
+
+    expect(mockUpdateNodeData).toHaveBeenCalledWith("test-prompt-1", {
+      prompt: "New prompt text",
+    });
+  });
+
+  it("should render the Prompt title", () => {
+    render(
+      <TestWrapper>
+        <PromptNode {...defaultProps} />
+      </TestWrapper>
+    );
+
+    expect(screen.getByText("Prompt")).toBeInTheDocument();
+  });
+});