Engineering

QA Engineer / SDET mock interview

The question that decides it is what you chose not to automate. Expect to defend a test strategy on cost rather than coverage, and to explain how you dealt with a suite so flaky the team stopped trusting it.

Also advertised as QA Engineer, SDET, Test Automation Engineer — the loop is the same, and so is the practice below.

Engineering loops are the most structured of any discipline, and the most predictable. Expect a recruiter screen, one or two technical rounds, a system design conversation at mid-level and above, and a behavioral round that is usually underestimated.

The technical rounds are rarely won on the answer. They are won on narration — whether the interviewer can follow your reasoning while you work, and whether you say the trade-off out loud instead of silently picking one.

The rounds you can practise

Each round is run by the interviewer built for it, with its own scoring axes — not one generic interviewer asked to change subject.

System design, trade-offs, and war stories from production.

Scored on Technical communication · Engineering depth · Ownership & collaboration

System design, trade-offs, and war stories from production.

Scored on Technical communication · Engineering depth · Ownership & collaboration

Hands-on problem solving, code quality, debugging, and engineering judgment.

Scored on Problem-solving communication · Engineering correctness · Adaptability & craft

System design, trade-offs, and war stories from production.

Scored on Technical communication · Engineering depth · Ownership & collaboration

Technical Deep-Dive

Theo · Principal Engineer

Hands-on problem solving, code quality, debugging, and engineering judgment.

Scored on Problem-solving communication · Engineering correctness · Adaptability & craft

QA Engineer / SDET interview questions

Six you can expect, in the register interviewers actually use. Answer them out loud before you read the next section — reading a question and answering one are different skills, and only the second is marked.

  1. What did you choose not to automate, and why?
  2. Your suite is flaky enough that the team ignores it. What do you do?
  3. How do you decide a release is ready when coverage is not complete?
  4. Design a test strategy for a checkout flow.
  5. How do you test something that depends on a third-party service?
  6. A bug reached production that your tests should have caught. What changes?

The same question, answered badly and well

The gap between these two is most of your score, and it is easier to see than to be told.

What did you choose not to automate, and why?

What loses marks

"We automated everything we could." It signals no cost model, and a suite built that way is the one the team eventually ignores.

What scores

A named area you left manual — rarely-changed, expensive to stub, low blast radius — with the maintenance cost you were avoiding and the risk you accepted instead. Test strategy is an economic argument, and this loop is testing whether you know that.

Why QA Engineer / SDET candidates get cut

The post-mortem nobody sends you. These are specific to this loop rather than general interview advice.

Coverage as a goal in itself, with no answer on what the number is protecting.
Treating flake as a nuisance rather than the most serious failure a suite can have — a test nobody trusts is worse than no test.
No view on where a test belongs. Everything at the end-to-end layer is the most common and most expensive mistake in this role.

Start with a general round

For QA Engineer / SDET, a general round runs with Kai system design, trade-offs, and war stories from production. It is the fastest way to find out which round you actually need to work on. The first session is free.

Practise a QA Engineer / SDET interview →

Question guides

Before you practise, it is worth reading how the common rounds are marked: tell me about yourself, behavioral questions and STAR, and system design.

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