Test(error): add empty-fallback checks and tests for root error boundaries

app/error.empty-fallback.test.tsx

@@ -0,0 +1,124 @@
+// app/error.empty-fallback.test.tsx
+
+import { describe, expect, it, vi, beforeEach } from 'vitest';
+import { render, screen, fireEvent } from '@testing-library/react';
+import '@testing-library/jest-dom/vitest';
+
+vi.mock('next/link', () => ({
+  default: ({
+    children,
+    ...props
+  }: React.AnchorHTMLAttributes<HTMLAnchorElement> & { children: React.ReactNode }) => (
+    <a {...props}>{children}</a>
+  ),
+}));
+
+vi.mock('sonner', () => ({
+  toast: {
+    success: vi.fn(),
+    error: vi.fn(),
+  },
+}));
+
+import ErrorBoundary from './error';
+
+describe('Root Error Boundary - Empty & Missing Input Fallbacks', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    // Mock clipboard API
+    Object.defineProperty(navigator, 'clipboard', {
+      value: {
+        writeText: vi.fn().mockResolvedValue(undefined),
+      },
+      configurable: true,
+      writable: true,
+    });
+  });
+
+  it('renders successfully when error is null', () => {
+    expect(() =>
+      render(<ErrorBoundary error={null as unknown as Error} reset={vi.fn()} />)
+    ).not.toThrow();
+
+    expect(
+      screen.getByRole('heading', {
+        name: /Looks like an exception was thrown in the application/i,
+      })
+    ).toBeInTheDocument();
+    expect(screen.getByText('Unknown runtime error occurred.')).toBeInTheDocument();
+  });
+
+  it('renders successfully when error is undefined', () => {
+    expect(() =>
+      render(<ErrorBoundary error={undefined as unknown as Error} reset={vi.fn()} />)
+    ).not.toThrow();
+
+    expect(
+      screen.getByRole('heading', {
+        name: /Looks like an exception was thrown in the application/i,
+      })
+    ).toBeInTheDocument();
+    expect(screen.getByText('Unknown runtime error occurred.')).toBeInTheDocument();
+  });
+
+  it('renders successfully when error is an empty object', () => {
+    expect(() =>
+      render(<ErrorBoundary error={{} as unknown as Error} reset={vi.fn()} />)
+    ).not.toThrow();
+
+    expect(
+      screen.getByRole('heading', {
+        name: /Looks like an exception was thrown in the application/i,
+      })
+    ).toBeInTheDocument();
+    expect(screen.getByText('Unknown runtime error occurred.')).toBeInTheDocument();
+  });
+
+  it('renders successfully when error has no message property', () => {
+    expect(() =>
+      render(<ErrorBoundary error={{ name: 'CustomError' } as unknown as Error} reset={vi.fn()} />)
+    ).not.toThrow();
+
+    expect(
+      screen.getByRole('heading', {
+        name: /Looks like an exception was thrown in the application/i,
+      })
+    ).toBeInTheDocument();
+    expect(screen.getByText('Unknown runtime error occurred.')).toBeInTheDocument();
+  });
+
+  it('renders successfully when error message is an empty string', () => {
+    expect(() => render(<ErrorBoundary error={new Error('')} reset={vi.fn()} />)).not.toThrow();
+
+    expect(
+      screen.getByRole('heading', {
+        name: /Looks like an exception was thrown in the application/i,
+      })
+    ).toBeInTheDocument();
+    expect(screen.getByText('Unknown runtime error occurred.')).toBeInTheDocument();
+  });
+
+  it('renders interactive elements and triggers actions correctly in fallback state', async () => {
+    const resetMock = vi.fn();
+    render(<ErrorBoundary error={{} as unknown as Error} reset={resetMock} />);
+
+    // Check actions
+    const retryButton = screen.getByRole('button', { name: /git fetch/i });
+    expect(retryButton).toBeInTheDocument();
+    fireEvent.click(retryButton);
+    expect(resetMock).toHaveBeenCalledOnce();
+
+    const homeLink = screen.getByRole('link', { name: /Return to main/i });
+    expect(homeLink).toBeInTheDocument();
+
+    // Check clipboard copy fallback behavior
+    const terminalContainer = screen.getByText('commitpulse — error').closest('div');
+    expect(terminalContainer).toBeInTheDocument();
+    if (terminalContainer) {
+      fireEvent.click(terminalContainer);
+      expect(navigator.clipboard.writeText).toHaveBeenCalledWith(
+        expect.stringContaining('Unknown exception in the render tree.')
+      );
+    }
+  });
+});

app/error.tsx

@@ -11,16 +11,20 @@ export default function ErrorBoundary({
   reset: () => void;
 }) {
   useEffect(() => {
-    console.error(error);
+    if (error) {
+      console.error(error);
+    }
   }, [error]);
 
+  const errorMessage = error?.message || '';
+
   const terminalContent = `git status
 
   fatal: Your branch and 'origin/main' have diverged,
   and have 1 and 1 different commits each, respectively.
 
   Error details:
-  ${error.message || 'Unknown exception in the render tree.'}`;
+  ${errorMessage || 'Unknown exception in the render tree.'}`;
 
   const handleCopy = async () => {
     try {
@@ -88,7 +92,7 @@ export default function ErrorBoundary({
               fatal: Your branch and 'origin/main' have diverged.
               <br />
               <span className="text-white/60 text-xs mt-2 block">
-                {error.message || 'Unknown runtime error occurred.'}
+                {errorMessage || 'Unknown runtime error occurred.'}
               </span>
             </p>
 

app/global-error.empty-fallback.test.tsx

@@ -0,0 +1,72 @@
+// app/global-error.empty-fallback.test.tsx
+
+import { describe, expect, it, vi } from 'vitest';
+import { render, screen, fireEvent } from '@testing-library/react';
+import '@testing-library/jest-dom/vitest';
+
+vi.mock('next/link', () => ({
+  default: ({
+    children,
+    ...props
+  }: React.AnchorHTMLAttributes<HTMLAnchorElement> & { children: React.ReactNode }) => (
+    <a {...props}>{children}</a>
+  ),
+}));
+
+import GlobalError from './global-error';
+
+describe('Global Error Page - Empty & Missing Input Fallbacks', () => {
+  it('renders successfully when error is null', () => {
+    expect(() =>
+      render(<GlobalError error={null as unknown as Error} reset={vi.fn()} />)
+    ).not.toThrow();
+
+    expect(screen.getByText('500')).toBeInTheDocument();
+    expect(screen.getByText('A critical error occurred at the root level.')).toBeInTheDocument();
+    expect(screen.getByText('Unknown global error')).toBeInTheDocument();
+  });
+
+  it('renders successfully when error is undefined', () => {
+    expect(() =>
+      render(<GlobalError error={undefined as unknown as Error} reset={vi.fn()} />)
+    ).not.toThrow();
+
+    expect(screen.getByText('500')).toBeInTheDocument();
+    expect(screen.getByText('Unknown global error')).toBeInTheDocument();
+  });
+
+  it('renders successfully when error is an empty object', () => {
+    expect(() =>
+      render(<GlobalError error={{} as unknown as Error} reset={vi.fn()} />)
+    ).not.toThrow();
+
+    expect(screen.getByText('500')).toBeInTheDocument();
+    expect(screen.getByText('Unknown global error')).toBeInTheDocument();
+  });
+
+  it('renders successfully when error has no message property', () => {
+    expect(() =>
+      render(<GlobalError error={{ name: 'CustomError' } as unknown as Error} reset={vi.fn()} />)
+    ).not.toThrow();
+
+    expect(screen.getByText('500')).toBeInTheDocument();
+    expect(screen.getByText('Unknown global error')).toBeInTheDocument();
+  });
+
+  it('renders successfully when error message is an empty string', () => {
+    expect(() => render(<GlobalError error={new Error('')} reset={vi.fn()} />)).not.toThrow();
+
+    expect(screen.getByText('500')).toBeInTheDocument();
+    expect(screen.getByText('Unknown global error')).toBeInTheDocument();
+  });
+
+  it('renders interactive elements and triggers reset correctly in fallback state', () => {
+    const resetMock = vi.fn();
+    render(<GlobalError error={{} as unknown as Error} reset={resetMock} />);
+
+    const retryButton = screen.getByRole('button', { name: /Try again/i });
+    expect(retryButton).toBeInTheDocument();
+    fireEvent.click(retryButton);
+    expect(resetMock).toHaveBeenCalledOnce();
+  });
+});

app/global-error.tsx

@@ -1,5 +1,4 @@
 'use client';
-import Link from 'next/link';
 
 export default function GlobalError({
   error,
@@ -8,6 +7,8 @@ export default function GlobalError({
   error: Error & { digest?: string };
   reset: () => void;
 }) {
+  const errorMessage = error?.message || '';
+
   return (
     <html lang="en">
       <body className="bg-black text-white antialiased">
@@ -17,7 +18,7 @@ export default function GlobalError({
             <p className="text-xl text-white/80">A critical error occurred at the root level.</p>
             <div className="p-4 bg-white/5 rounded-xl border border-white/10 text-left w-full overflow-auto">
               <code className="text-sm text-red-400 font-mono">
-                {error.message || 'Unknown global error'}
+                {errorMessage || 'Unknown global error'}
               </code>
             </div>
             <button