6 files changed, 228 insertions, 0 deletions
diff --git a/src/lib/constants.test.ts b/src/lib/constants.test.ts
new file mode 100644
index 0000000..65fb466
--- /dev/null
+++ b/src/lib/constants.test.ts
@@ -0,0 +1,54 @@
+import { afterAll, beforeEach, describe, expect, test, vi } from 'vitest';
+
+const originalEnv = process.env;
+
+function setEnv(key: string, value?: string) {
+  if (value === undefined) {
+    delete process.env[key];
+    return;
+  }
+
+  process.env[key] = value;
+}
+
+describe('constants', () => {
+  beforeEach(() => {
+    vi.resetModules();
+    process.env = { ...originalEnv };
+  });
+
+  afterAll(() => {
+    process.env = originalEnv;
+  });
+
+  test('uses localhost base url outside production', async () => {
+    setEnv('NODE_ENV', 'development');
+    setEnv('VERCEL_PROJECT_PRODUCTION_URL', 'example.com');
+
+    const constants = await import('./constants');
+
+    expect(constants.isProduction).toBe(false);
+    expect(constants.baseUrl.href).toBe('http://localhost:3000/');
+  });
+
+  test('uses vercel production url in production', async () => {
+    setEnv('NODE_ENV', 'production');
+    setEnv('VERCEL_PROJECT_PRODUCTION_URL', 'blog.example.com');
+
+    const constants = await import('./constants');
+
+    expect(constants.isProduction).toBe(true);
+    expect(constants.baseUrl.href).toBe('https://blog.example.com/');
+  });
+
+  test('falls back to localhost when production url is missing', async () => {
+    setEnv('NODE_ENV', 'production');
+    setEnv('VERCEL_PROJECT_PRODUCTION_URL');
+
+    const constants = await import('./constants');
+
+    expect(constants.isProduction).toBe(true);
+    expect(constants.baseUrl.href).toBe('http://localhost:3000/');
+  });
+});
+
diff --git a/src/lib/is-active.test.ts b/src/lib/is-active.test.ts
new file mode 100644
index 0000000..fcc42d0
--- /dev/null
+++ b/src/lib/is-active.test.ts
@@ -0,0 +1,26 @@
+import { describe, expect, test } from 'vitest';
+import { isActive } from './is-active';
+
+describe('isActive', () => {
+  test('returns true for exact match', () => {
+    expect(isActive('/posts', '/posts')).toBe(true);
+  });
+
+  test('normalizes trailing slashes before comparing', () => {
+    expect(isActive('/posts/', '/posts')).toBe(true);
+    expect(isActive('/posts', '/posts/')).toBe(true);
+  });
+
+  test('returns true for nested paths when nested is enabled', () => {
+    expect(isActive('/posts', '/posts/hello-world', true)).toBe(true);
+  });
+
+  test('returns false for nested paths when nested is disabled', () => {
+    expect(isActive('/posts', '/posts/hello-world', false)).toBe(false);
+  });
+
+  test('returns false for unrelated paths', () => {
+    expect(isActive('/posts', '/tags')).toBe(false);
+  });
+});
+
diff --git a/src/lib/metadata.test.ts b/src/lib/metadata.test.ts
new file mode 100644
index 0000000..ce5c5b0
--- /dev/null
+++ b/src/lib/metadata.test.ts
@@ -0,0 +1,58 @@
+import { describe, expect, test } from 'vitest';
+import { createMetadata } from './metadata';
+
+describe('createMetadata', () => {
+  test('builds metadata with default open graph, twitter, and alternates fields', () => {
+    const metadata = createMetadata({
+      title: 'My Post',
+      description: 'Post description',
+    });
+
+    expect(metadata.openGraph).toMatchObject({
+      title: 'My Post',
+      description: 'Post description',
+      url: 'https://blog.techwithanirudh.com',
+      images: '/banner.png',
+      siteName: 'Blog',
+    });
+
+    expect(metadata.twitter).toMatchObject({
+      card: 'summary_large_image',
+      creator: '@AnirudhWith',
+      title: 'My Post',
+      description: 'Post description',
+      images: '/banner.png',
+    });
+
+    expect(metadata.alternates).toMatchObject({
+      canonical: '/',
+      types: {
+        'application/rss+xml': '/api/rss.xml',
+      },
+    });
+  });
+
+  test('allows nested metadata fields to override defaults and top-level fallbacks', () => {
+    const metadata = createMetadata({
+      title: 'Top Level Title',
+      openGraph: {
+        title: 'OG Title',
+        url: 'https://example.com/posts/1',
+      },
+      twitter: {
+        title: 'Twitter Title',
+        card: 'summary',
+      },
+      alternates: {
+        canonical: '/posts/1',
+      },
+    });
+
+    expect(metadata.openGraph?.title).toBe('OG Title');
+    expect(metadata.openGraph?.url).toBe('https://example.com/posts/1');
+    expect(metadata.twitter?.title).toBe('Twitter Title');
+    expect(metadata.twitter?.card).toBe('summary');
+    expect(metadata.alternates?.canonical).toBe('/posts/1');
+  });
+});
+
diff --git a/src/lib/safe-action.test.ts b/src/lib/safe-action.test.ts
new file mode 100644
index 0000000..eee5679
--- /dev/null
+++ b/src/lib/safe-action.test.ts
@@ -0,0 +1,42 @@
+import { afterEach, describe, expect, test, vi } from 'vitest';
+
+vi.mock('next-safe-action', () => ({
+  DEFAULT_SERVER_ERROR_MESSAGE: 'Internal server error',
+  createSafeActionClient: vi.fn((options: unknown) => options),
+}));
+
+describe('safe-action', () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+    vi.resetModules();
+  });
+
+  test('returns custom message for ActionError', async () => {
+    const errorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+    const { ActionError, actionClient } = await import('./safe-action');
+    const client = actionClient as unknown as {
+      handleServerError: (e: Error) => string;
+    };
+
+    const message = client.handleServerError(new ActionError('Custom error'));
+
+    expect(message).toBe('Custom error');
+    expect(errorSpy).toHaveBeenCalledWith(
+      'Failed to execute action:',
+      'Custom error',
+    );
+  });
+
+  test('returns default message for unknown errors', async () => {
+    const errorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+    const { actionClient } = await import('./safe-action');
+    const client = actionClient as unknown as {
+      handleServerError: (e: Error) => string;
+    };
+
+    const message = client.handleServerError(new Error('Unexpected'));
+
+    expect(message).toBe('Internal server error');
+    expect(errorSpy).toHaveBeenCalledWith('Failed to execute action:', 'Unexpected');
+  });
+});
diff --git a/src/lib/utils.test.ts b/src/lib/utils.test.ts
new file mode 100644
index 0000000..9a61d41
--- /dev/null
+++ b/src/lib/utils.test.ts
@@ -0,0 +1,21 @@
+import { describe, expect, test } from 'vitest';
+import { cn } from './utils';
+
+describe('cn', () => {
+  test('merges class names and resolves tailwind conflicts', () => {
+    expect(cn('px-2', 'px-4')).toBe('px-4');
+  });
+
+  test('handles conditional and falsy inputs', () => {
+    expect(cn('text-sm', false && 'hidden', undefined, 'font-medium')).toBe(
+      'text-sm font-medium',
+    );
+  });
+
+  test('supports object and array style class inputs', () => {
+    expect(
+      cn(['inline-flex', ['items-center']], { 'cursor-pointer': true }),
+    ).toBe('inline-flex items-center cursor-pointer');
+  });
+});
+
diff --git a/src/lib/validators/newsletter.test.ts b/src/lib/validators/newsletter.test.ts
new file mode 100644
index 0000000..12e3f46
--- /dev/null
+++ b/src/lib/validators/newsletter.test.ts
@@ -0,0 +1,27 @@
+import { describe, expect, test } from 'vitest';
+import { NewsletterSchema } from './newsletter';
+
+describe('NewsletterSchema', () => {
+  test('accepts a valid email payload', () => {
+    const parsed = NewsletterSchema.parse({
+      email: 'user@example.com',
+    });
+
+    expect(parsed).toEqual({ email: 'user@example.com' });
+  });
+
+  test('rejects invalid email payloads', () => {
+    expect(
+      NewsletterSchema.safeParse({
+        email: 'invalid-email',
+      }).success,
+    ).toBe(false);
+
+    expect(
+      NewsletterSchema.safeParse({
+        email: '',
+      }).success,
+    ).toBe(false);
+  });
+});
+