test(notification): add error resilience tests

Author: pari7maheshwari

models/Notification.error-resilience.test.ts

@@ -0,0 +1,101 @@
+import mongoose from 'mongoose';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+describe('Notification error resilience', () => {
+  beforeEach(() => {
+    vi.resetModules();
+    vi.restoreAllMocks();
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('should safely reuse existing Notification model during hydration', async () => {
+    vi.resetModules();
+
+    const existingModel = { mocked: true };
+
+    mongoose.models.Notification = existingModel as never;
+
+    const { Notification } = await import('./Notification');
+
+    expect(Notification).toBe(existingModel);
+  });
+
+  it('should recover cleanly when mongoose.model throws unexpectedly', async () => {
+    vi.resetModules();
+
+    // Force recreation instead of reusing cached model
+    delete mongoose.models.Notification;
+
+    vi.spyOn(mongoose, 'model').mockImplementation(() => {
+      throw new Error('Database connectivity error');
+    });
+
+    let caughtError: Error | null = null;
+
+    try {
+      await import('./Notification');
+    } catch (error) {
+      caughtError = error as Error;
+    }
+
+    expect(caughtError).toBeTruthy();
+    expect(caughtError?.message).toContain('Database connectivity error');
+  });
+
+  it('should expose safe default values for recovery stability', async () => {
+    vi.resetModules();
+
+    delete mongoose.models.Notification;
+
+    const { Notification } = await import('./Notification');
+
+    const doc = new Notification({
+      username: 'pari',
+      email: 'pari@example.com',
+    });
+
+    expect(doc.frequency).toBe('daily');
+    expect(doc.notifyOnCommit).toBe(true);
+    expect(doc.notifyOnStreak).toBe(true);
+    expect(doc.notifyOnMilestone).toBe(true);
+    expect(doc.isActive).toBe(true);
+  });
+
+  it('should prevent invalid frequency values from crashing validation', async () => {
+    vi.resetModules();
+
+    delete mongoose.models.Notification;
+
+    const { Notification } = await import('./Notification');
+
+    const doc = new Notification({
+      username: 'pari',
+      email: 'pari@example.com',
+      frequency: 'invalid-value',
+    });
+
+    const validationError = doc.validateSync();
+
+    expect(validationError).toBeTruthy();
+    expect(validationError?.errors.frequency).toBeDefined();
+  });
+
+  it('should keep required validation failures localized', async () => {
+    vi.resetModules();
+
+    delete mongoose.models.Notification;
+
+    const { Notification } = await import('./Notification');
+
+    const doc = new Notification({});
+
+    const validationError = doc.validateSync();
+
+    expect(validationError).toBeTruthy();
+    expect(validationError?.errors.username).toBeDefined();
+    expect(validationError?.errors.email).toBeDefined();
+  });
+});