Mock SDET Interview: What Every Junior QA Should Know

So, you’re getting ready for your first QA/SDET interview?

I’ve been there — and let me tell you, it’s not just about answering questions. It’s about proving that you can think like an engineer, handle pressure, and show that you’ll add value to a dev team.

That’s exactly why mock interviews are game-changers. They let you practice in a safe space, make mistakes, and get feedback before it really counts.

Here’s a breakdown of real Junior QA / SDET interview questions I’ve seen — plus tips on how to nail them.

Common Questions You’ll Hear in a Junior SDET Interview

1. Tell me about yourself.

👉 Keep it short: Present → Past → Future.
💡 Example:

“I just wrapped up a QA training program where I worked with Playwright and JavaScript. Before that, I was in logistics, where I learned process optimization. Now I’m looking for a Junior SDET role where I can grow in automation and testing.”

2. QA vs QC vs Testing — what’s the difference?

QA = process (preventing bugs)

QC = product check (validating results)

Testing = actually finding issues

💡 Quick answer:

“QA ensures the process, QC checks the result, and testing is the execution. All three matter.”

3. Write a test case for a login page.

Structure is key:

Test Case: Login with valid credentials

Precondition: user exists.

Steps: open login page → enter email + password → click login.

Expected result: user lands on dashboard.

4. Write a short program to reverse a string.

💡 JavaScript example:

function reverseString(str) {
return str.split('').reverse().join('');
}
console.log(reverseString("Interview")); // weivretnI

Don’t just write the code — explain your thinking. That’s what they’re really checking.

5. How do you test an API?

Checklist to mention:

Status codes (200, 400, 500)

Response body (fields, types)

Headers (auth, content type)

Negative cases (invalid input)

💡 Example:

“I start with Postman to validate positive and negative scenarios, then automate with Playwright or RestAssured.”

6. Selenium vs Cypress vs Playwright

Selenium: legacy, multi-language, slower.

Cypress: modern, JS-only, fast, fewer browsers.

Playwright: modern, multi-language, multi-browser, API + UI.

💡 Example:

“I prefer Playwright for speed + CI/CD, but Selenium is still common in older projects.”

7. How do you handle conflicts with developers?

💡 Example:

“I don’t argue — I bring evidence. Logs, repro steps, impact. My role is to help ship quality, not to ‘win’ the argument.”

Why You Should Do a Mock Interview

Practice without risk.

Get honest feedback.

Build confidence before it’s real.

When the actual interview comes, you’ll feel like you’ve already been there.

Over to You

Have you ever done a mock interview before your real one?

What’s the hardest question you’ve faced in a Junior QA/SDET interview?

Drop your thoughts in the comments 👇 Let’s make this a resource for every new QA engineer out there.