test: add unit tests for Notification model (JhaSourav07#3549)

## Description

This PR implements unit tests for the Notification mongoose schema,
verifying compile validity, path definitions, required and unique
properties, enum values, default booleans, and timestamp declarations.

Fixes JhaSourav07#3458

## Pillar

- [ ] 🎨 Pillar 1 — New Theme Design
- [ ] 📐 Pillar 2 — Geometric SVG Improvement
- [ ] 🕐 Pillar 3 — Timezone Logic Optimization
- [x] 🛠️ Other (Bug fix, refactoring, docs)

## Visual Preview

N/A (Utility/Unit Tests only)

## Checklist before requesting a review:

- [x] I have read the `CONTRIBUTING.md` file.
- [x] I have tested these changes locally.
- [x] I have run `npm run format` and `npm run lint` locally and
resolved all errors.
- [x] My commits follow the Conventional Commits format.
- [x] I have updated `README.md` if I added a new theme or URL
parameter.
- [x] I have started the repo.
- [x] I have made sure that i have only one commit to merge in this PR.
- [ ] The SVG output matches the CommitPulse "premium quality" aesthetic
standard.
- [ ] (Recommended) I joined the CommitPulse Discord community.

Author: JhaSourav07

models/Notification.test.ts

@@ -0,0 +1,83 @@
+import mongoose from 'mongoose';
+import { describe, it, expect } from 'vitest';
+import { Notification } from './Notification';
+
+describe('Notification Model', () => {
+  it('is compiled properly and exposed', () => {
+    expect(Notification).toBeDefined();
+    expect(Notification.modelName).toBe('Notification');
+  });
+
+  it('enforces required, unique, and lowercase fields on username', () => {
+    const usernamePath = Notification.schema.path('username') as mongoose.SchemaType & {
+      options: Record<string, unknown>;
+    };
+
+    expect(usernamePath).toBeDefined();
+    expect(usernamePath.options.required).toBe(true);
+    expect(usernamePath.options.unique).toBe(true);
+    expect(usernamePath.options.lowercase).toBe(true);
+    expect(usernamePath.options.trim).toBe(true);
+  });
+
+  it('enforces required, lowercase, and trim fields on email', () => {
+    const emailPath = Notification.schema.path('email') as mongoose.SchemaType & {
+      options: Record<string, unknown>;
+    };
+
+    expect(emailPath).toBeDefined();
+    expect(emailPath.options.required).toBe(true);
+    expect(emailPath.options.lowercase).toBe(true);
+    expect(emailPath.options.trim).toBe(true);
+  });
+
+  it('validates frequency field and its defaults and enums', () => {
+    const frequencyPath = Notification.schema.path('frequency') as mongoose.SchemaType & {
+      options: Record<string, unknown>;
+      enumValues: string[];
+    };
+
+    expect(frequencyPath).toBeDefined();
+    expect(frequencyPath.options.default).toBe('daily');
+    expect(frequencyPath.enumValues).toContain('realtime');
+    expect(frequencyPath.enumValues).toContain('daily');
+    expect(frequencyPath.enumValues).toContain('weekly');
+  });
+
+  it('checks boolean notification switches have default value as true', () => {
+    const notifyOnCommitPath = Notification.schema.path('notifyOnCommit') as mongoose.SchemaType & {
+      options: Record<string, unknown>;
+    };
+    const notifyOnStreakPath = Notification.schema.path('notifyOnStreak') as mongoose.SchemaType & {
+      options: Record<string, unknown>;
+    };
+    const notifyOnMilestonePath = Notification.schema.path(
+      'notifyOnMilestone'
+    ) as mongoose.SchemaType & {
+      options: Record<string, unknown>;
+    };
+
+    expect(notifyOnCommitPath.options.default).toBe(true);
+    expect(notifyOnStreakPath.options.default).toBe(true);
+    expect(notifyOnMilestonePath.options.default).toBe(true);
+  });
+
+  it('checks isActive default value is true', () => {
+    const isActivePath = Notification.schema.path('isActive') as mongoose.SchemaType & {
+      options: Record<string, unknown>;
+    };
+    expect(isActivePath.options.default).toBe(true);
+  });
+
+  it('checks createdAt and updatedAt have default values', () => {
+    const createdAtPath = Notification.schema.path('createdAt') as mongoose.SchemaType & {
+      options: Record<string, unknown>;
+    };
+    const updatedAtPath = Notification.schema.path('updatedAt') as mongoose.SchemaType & {
+      options: Record<string, unknown>;
+    };
+
+    expect(createdAtPath.options.default).toBeDefined();
+    expect(updatedAtPath.options.default).toBeDefined();
+  });
+});