test: подключить vitest и покрыть утилиты юнит-тестами

src/utils/validation.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, it } from 'vitest';
+import { isValidEmail } from './validation';
+
+describe('isValidEmail', () => {
+  it('accepts common addresses', () => {
+    expect(isValidEmail('user@example.com')).toBe(true);
+    expect(isValidEmail('a.b+tag@sub.domain.io')).toBe(true);
+  });
+
+  it('rejects malformed addresses', () => {
+    expect(isValidEmail('')).toBe(false);
+    expect(isValidEmail('plain')).toBe(false);
+    expect(isValidEmail('user@host')).toBe(false);
+    expect(isValidEmail('user @example.com')).toBe(false);
+    expect(isValidEmail('user@exa mple.com')).toBe(false);
+  });
+});