Email Regex Validation in Test Automation — Do It Right

2026-07-17 · By Avinash Kamble, reviewed by Priyanka G.

Every signup form has an email field. Testing it well means picking a pragmatic regex and covering the boundary cases — not writing a 6,000-character RFC 5322 monster.

^[\w.+-]+@[\w-]+\.[\w.-]+$

Covers 99% of real-world addresses; rejects the obvious garbage. Test it in the Regex Tester for QA before shipping.

VALID
a@b.co
first.last+tag@example.com
user_name@sub.example.co.uk

INVALID
plaintext
@nodomain.com
name@.com
name@domain
name@@domain.com
name domain@example.com

const invalidEmails = ['plain', '@no.com', 'a@b'];
for (const email of invalidEmails) {
  await page.getByLabel('Email').fill(email);
  await page.getByRole('button', { name: 'Sign up' }).click();
  await expect(page.getByText('Enter a valid email')).toBeVisible();
}

A well-formed email doesn't mean a deliverable email. Also verify: MX record checks, disposable-domain blocking, and confirmation email delivery. Regex is the cheap first gate.