Test: verify edge cases and empty inputs for compare API route

app/api/compare/route.empty-fallback.test.ts

@@ -0,0 +1,71 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { GET } from './route';
+
+vi.mock('@/lib/github', () => ({
+  getFullDashboardData: vi.fn(),
+}));
+
+import { getFullDashboardData } from '@/lib/github';
+
+function makeRequest(search: string, headers: Record<string, string> = {}): Request {
+  return new Request(`http://localhost:3000/api/compare?${search}`, { headers });
+}
+
+describe('GET /api/compare - Empty & Missing Input Fallbacks', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('returns 400 when user1 is an empty string', async () => {
+    const res = await GET(makeRequest('user1=&user2=octocat'));
+    expect(res.status).toBe(400);
+    const data = await res.json();
+    expect(data.error).toBe('Invalid parameters');
+    expect(data.details.fieldErrors.user1).toBeDefined();
+  });
+
+  it('returns 400 when user2 is only whitespace', async () => {
+    const res = await GET(makeRequest('user1=octocat&user2=%20%20%20'));
+    expect(res.status).toBe(400);
+    const data = await res.json();
+    expect(data.error).toBe('Invalid parameters');
+    expect(data.details.fieldErrors.user2).toBeDefined();
+  });
+
+  it('returns 400 when query string is completely empty', async () => {
+    const res = await GET(makeRequest(''));
+    expect(res.status).toBe(400);
+    const data = await res.json();
+    expect(data.error).toBe('Invalid parameters');
+    expect(data.details.fieldErrors.user1).toBeDefined();
+    expect(data.details.fieldErrors.user2).toBeDefined();
+  });
+
+  it('handles empty/minimal dashboard response from upstream gracefully', async () => {
+    vi.mocked(getFullDashboardData).mockResolvedValue({} as never);
+
+    const res = await GET(makeRequest('user1=alice&user2=bob'));
+    expect(res.status).toBe(200);
+
+    const data = await res.json();
+    expect(data.user1).toEqual({});
+    expect(data.user2).toEqual({});
+  });
+
+  it('returns 200 and includes ETag/Cache-Control when If-None-Match header is missing', async () => {
+    vi.mocked(getFullDashboardData).mockResolvedValue({ profile: { username: 'test' } } as never);
+
+    const res = await GET(makeRequest('user1=alice&user2=bob'));
+    expect(res.status).toBe(200);
+    expect(res.headers.get('ETag')).toBeTruthy();
+    expect(res.headers.get('Cache-Control')).toBe('public, s-maxage=3600');
+  });
+
+  it('returns 200 when If-None-Match is an empty string instead of crashing', async () => {
+    vi.mocked(getFullDashboardData).mockResolvedValue({ profile: { username: 'test' } } as never);
+
+    const res = await GET(makeRequest('user1=alice&user2=bob', { 'if-none-match': '' }));
+    expect(res.status).toBe(200);
+    expect(res.headers.get('ETag')).toBeTruthy();
+  });
+});