diff --git a/src/__tests__/version-check.test.ts b/src/__tests__/version-check.test.ts
new file mode 100644
index 0000000..d5d30c1
--- /dev/null
+++ b/src/__tests__/version-check.test.ts
@@ -0,0 +1,100 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { compareSemver, getUpdateType, checkForUpdates } from '../utils/version-check';
+import { logger } from '../utils/logger';
+
+vi.mock('../utils/logger', () => ({
+  logger: {
+    error: vi.fn(),
+  },
+}));
+
+describe('version-check utilities', () => {
+  describe('compareSemver', () => {
+    it('should return "lt" if a < b', () => {
+      expect(compareSemver('1.0.0', '1.0.1')).toBe('lt');
+      expect(compareSemver('1.0.0', '1.1.0')).toBe('lt');
+      expect(compareSemver('1.0.0', '2.0.0')).toBe('lt');
+    });
+
+    it('should return "gt" if a > b', () => {
+      expect(compareSemver('1.0.1', '1.0.0')).toBe('gt');
+      expect(compareSemver('1.1.0', '1.0.0')).toBe('gt');
+      expect(compareSemver('2.0.0', '1.0.0')).toBe('gt');
+    });
+
+    it('should return "eq" if a === b', () => {
+      expect(compareSemver('1.0.0', '1.0.0')).toBe('eq');
+      expect(compareSemver('v1.0.0', '1.0.0')).toBe('eq');
+    });
+  });
+
+  describe('getUpdateType', () => {
+    it('should return "major" for major updates', () => {
+      expect(getUpdateType('1.0.0', '2.0.0')).toBe('major');
+    });
+
+    it('should return "minor" for minor updates', () => {
+      expect(getUpdateType('1.0.0', '1.1.0')).toBe('minor');
+    });
+
+    it('should return "patch" for patch updates', () => {
+      expect(getUpdateType('1.0.0', '1.0.1')).toBe('patch');
+    });
+
+    it('should return empty string if versions are equal', () => {
+      expect(getUpdateType('1.0.0', '1.0.0')).toBe('');
+    });
+
+    it('should return empty string for downgrades', () => {
+      expect(getUpdateType('2.0.0', '1.0.0')).toBe('');
+      expect(getUpdateType('1.1.0', '1.0.0')).toBe('');
+      expect(getUpdateType('1.0.1', '1.0.0')).toBe('');
+    });
+  });
+
+  describe('checkForUpdates', () => {
+    const fetchMock = vi.fn();
+    
+    beforeEach(() => {
+      vi.stubGlobal('fetch', fetchMock);
+      vi.spyOn(console, 'log').mockImplementation(() => {});
+    });
+
+    afterEach(() => {
+      vi.unstubAllGlobals();
+      vi.restoreAllMocks();
+    });
+
+    it('should log an error if registry response is invalid', async () => {
+      fetchMock.mockResolvedValue({
+        ok: true,
+        json: () => Promise.resolve({ not_a_version: '1.2.3' }),
+      });
+
+      await checkForUpdates();
+
+      expect(logger.error).toHaveBeenCalledWith(expect.stringContaining('Invalid registry response'));
+    });
+
+    it('should handle fetch timeout/error gracefully', async () => {
+      fetchMock.mockRejectedValue(new Error('Timeout'));
+
+      await checkForUpdates();
+      // Should not throw and should not log error (it fails silently in the catch block for network errors)
+      expect(logger.error).not.toHaveBeenCalled();
+    });
+
+    it('should log update message if a newer version is available', async () => {
+      fetchMock.mockResolvedValue({
+        ok: true,
+        json: () => Promise.resolve({ version: '9.9.9' }),
+      });
+
+      const consoleSpy = vi.spyOn(console, 'log');
+      await checkForUpdates();
+
+      expect(consoleSpy).toHaveBeenCalledWith(expect.stringContaining('update available!'));
+      expect(consoleSpy).toHaveBeenCalledWith(expect.stringContaining('v9.9.9'));
+    });
+  });
+});
diff --git a/src/utils/version-check.ts b/src/utils/version-check.ts
index 618ed32..528f1f1 100644
--- a/src/utils/version-check.ts
+++ b/src/utils/version-check.ts
@@ -2,6 +2,7 @@ import chalk from 'chalk';
 import { readFileSync } from 'node:fs';
 import { fileURLToPath } from 'node:url';
 import { dirname, join } from 'node:path';
+import { logger } from './logger';
 
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = dirname(__filename);
@@ -18,7 +19,7 @@ function getInstalledVersion(): string {
 }
 
 // Compare two semver strings; returns 'lt' if a < b, 'gt' if a > b, 'eq' if equal
-function compareSemver(a: string, b: string): 'lt' | 'gt' | 'eq' {
+export function compareSemver(a: string, b: string): 'lt' | 'gt' | 'eq' {
   const parse = (v: string) => v.replace(/^v/, '').split('.').map(Number);
   const [a1, a2, a3] = parse(a);
   const [b1, b2, b3] = parse(b);
@@ -29,23 +30,15 @@ function compareSemver(a: string, b: string): 'lt' | 'gt' | 'eq' {
 }
 
 // Determine update type for messaging
-function getUpdateType(installed: string, latest: string): string {
+export function getUpdateType(installed: string, latest: string): string {
   const cmp = compareSemver(installed, latest);
-  if (cmp === 'eq') return '';
-  const [i1] = installed.replace(/^v/, '').split('.').map(Number);
-  const [l1] = latest.replace(/^v/, '').split('.').map(Number);
-  if (l1 > i1) return 'major';
-function getUpdateType(installed: string, latest: string): string {
-  const cmp = compareSemver(installed, latest);
-  if (cmp === 'eq') return '';
+  if (cmp === 'eq' || cmp === 'gt') return '';
   const [i1 = 0, i2 = 0] = installed.replace(/^v/, '').split('.').map(Number);
   const [l1 = 0, l2 = 0] = latest.replace(/^v/, '').split('.').map(Number);
   if (l1 > i1) return 'major';
   if (l2 > i2) return 'minor';
   return 'patch';
 }
-  return 'patch';
-}
 
 export async function checkForUpdates(): Promise<void> {
   try {
@@ -54,7 +47,13 @@ export async function checkForUpdates(): Promise<void> {
     });
     if (!response.ok) return;
 
-    const data = await response.json() as { version: string };
+    const data = (await response.json()) as unknown;
+    
+    if (!data || typeof data !== 'object' || !('version' in data) || typeof data.version !== 'string') {
+      logger.error('Invalid registry response: version not found');
+      return;
+    }
+
     const latestVersion = data.version;
     const installedVersion = getInstalledVersion();