✅ Add tests for env validation

src/env.spec.ts

@@ -0,0 +1,11 @@
+import { describe, expect, it, vi } from 'vitest';
+
+import { env } from './env';
+
+describe('environment validation', () => {
+  it('test', () => {
+    vi.stubEnv('PORT', '9876')
+
+    expect(env.NEXT_PUBLIC_PORT).toBe(9876);
+  });
+});