QA and SDET careers: skills and certifications
Understand the difference between manual QA, automation engineer, SDET and performance tester roles, which skills to build in what order, how to show your work, and what to expect in interviews and certifications.
Testing is often seen as an entry door into software, but it is also a long career. Good testers protect users and money, and teams value people who find problems early and automate the boring parts. The titles vary between companies, so read the job description, not just the name.
This lesson describes common roles, a skill roadmap you can follow with this track, how to build proof of skill, and the interview questions to practise. It does not promise salaries or hiring numbers, because those change by city, company and year. Check current job listings for realistic expectations.
The roles
Common roles
| Role | What you do day to day | Main skills |
|---|---|---|
| Manual QA / test engineer | Read requirements, design and run test cases, explore the product, report bugs | Test design, attention to detail, communication, API tools like Postman |
| QA automation engineer | Write and maintain automated UI and API tests, run them in CI | A language (Python, Java, JavaScript), Playwright or Selenium, API automation |
| SDET (software development engineer in test) | Build test frameworks, tools and pipelines; review code; test at every level | Strong programming, design patterns, CI/CD, mocking, reading application code |
| Performance tester | Design load tests, find bottlenecks, report capacity | k6 or JMeter, monitoring, databases, networking basics |
| Security tester (QA side) | Run scans and checks for common weaknesses | OWASP Top 10, ZAP, threat thinking. Deeper work is a separate security career |
| QA lead / manager | Plan strategy, guide the team, report quality to stakeholders | Strategy, people skills, metrics |
The name "SDET" is used differently by different companies. At some it means a developer who specialises in test infrastructure; at others it simply means automation engineer. The practical difference is how much programming and design the job expects. If you like coding, aim for SDET-style roles. If you like investigating products and users, strong exploratory skills are just as valuable. Many people start in manual QA and move to automation within a year or two, but nothing guarantees it, so build the automation skills yourself.
A skill roadmap
A sensible order (this track covers most of it)
- 1Testing basics: the test pyramid, types of testing, writing test cases and bug reports (see *Why we test* and *Designing test cases*).
- 2API testing by hand: curl, browser dev tools, Postman or Bruno. Understand HTTP methods, status codes, JSON and headers.
- 3One programming language, well: Python or JavaScript is enough. Functions, lists and dictionaries, files, exceptions, packages.
- 4Unit and API automation: pytest or Vitest, fixtures, parametrized tests, an HTTP client library.
- 5Mocks and integration tests: test doubles, databases in tests, contract tests.
- 6End-to-end tests: Playwright, stable locators, the page object pattern.
- 7CI/CD and Git: GitHub Actions, pull requests, reading failed runs.
- 8Non-functional testing: a first load test with k6 and a baseline scan with ZAP.
- 9SQL and Linux basics: query a database to check data, read logs, use the terminal.
- 10Strategy and communication: risk thinking, clear bug reports, explaining quality to non-testers.
Learn principles, not just tools
Skills that last: understanding how software works, writing clear bug reports and thinking about risk. Tools change every few years, and a learner who knows *why* a test exists can pick up any new tool quickly.
Show your work
Recruiters see many resumes that list "Selenium, Postman, JIRA". What stands out is evidence. Build a small portfolio:
- A GitHub repository with an API test suite and a working CI badge, like *Project: a full test suite for a coffee shop API*. Include a README that explains what is covered and how to run it. - A Playwright end-to-end repository testing a public demo site or your own project. - A short written test strategy or bug report sample (without any employer's confidential information). - Real bugs found in open-source or practice sites, written up clearly.
On your resume, describe results and scope in plain words: "Wrote 40 API tests for an ordering API with boundary and state tests; run in GitHub Actions on every pull request." Only claim what you did and can explain.
Be able to explain every line
Do not copy test projects from the internet and present them as your own. Interviewers often ask you to explain a test line by line, or to change it live. Build your own, even if it is small.
Interview questions to practise
Common questions
| Question | What a good answer includes |
|---|---|
| What is the difference between severity and priority? | Severity is the impact of the defect; priority is how soon the business wants it fixed. Give an example of high severity with low priority |
| How would you test a login page or a payment API? | Clarify requirements, then positive, negative, boundary, security, performance and usability cases |
| What is the difference between 400, 401, 403 and 404? | Bad request, not authenticated, not allowed, not found |
| What would you automate and what not? | Repeatable, stable, high-value checks; not one-off, quickly changing or exploratory checks |
| What is a flaky test and how do you deal with it? | Passes and fails without code change; find the cause (timing, shared data), fix or quarantine |
| What is the difference between a mock and a stub? | See *Mocks, stubs and test doubles* |
| Write a function that finds duplicates in a list | Basic coding; SDET roles often have a coding round |
| Tell me about a bug you found | Situation, how you found it, how you reported it, what changed |
Act as an interviewer for a [QA automation engineer / SDET] role at an Indian product company. I am a [fresher / 2 years experience] with skills in [list]. Ask me one question at a time: start with testing fundamentals, then API testing, then automation code, then a scenario question. After each answer, give feedback on correctness and clarity and one thing to improve, then ask the next question. Stop after 8 questions and give an overall summary.What to expect: Answer out loud or in writing before reading feedback. You can also practise full mock interviews in InterviewAI.
Certifications
Certificates help most when you have no experience, and when a company screens by them. They never replace a portfolio. Always check the provider's official page for the current name, syllabus and fee, because these change.
A short list (verify details on official pages)
| Certification | Suits | Notes |
|---|---|---|
| ISTQB Certified Tester Foundation Level (CTFL) | Freshers and manual testers | The most widely recognised starting point. Syllabus and sample papers are on istqb.org. An exam fee applies; in India, exams are typically booked through the national board or an approved exam provider, so check the official page |
| ISTQB advanced and specialist modules (for example test automation or AI testing) | People with some experience | Take after you have worked in testing; some require CTFL first |
| Vendor learning badges, such as Postman's free API courses | Beginners who want a quick proof of API skills | Check the provider's page for what is currently free and what the badge means |
| Cloud basics (AWS, Azure or Google Cloud fundamentals) | Testers moving to SDET or DevOps-adjacent roles | Optional, and useful if your team tests cloud systems |
There are also training courses and paid bootcamps. Be careful with anything that promises a job. Compare the syllabus with what this track teaches, read independent reviews, and prefer options that make you build things.
Habits of a strong tester
Daily habits
- Ask "what could go wrong?" and "what did we not think of?"
- Write bug reports that someone can reproduce in two minutes.
- Learn the product and its users, not only the test tools.
- Read code, even if you don't write production code.
- Automate the repetitive checks and keep time for exploring.
- Keep notes on bugs you find, and review what kinds of bugs escape.
- Stay curious about AI: use it to speed up your work, and learn to test AI features (see *Testing with AI, and testing AI features*).
Try it: Your 90-day plan
Write a plan for the next 90 days using the roadmap. For each month choose one outcome you can show on GitHub, for example: month 1, a Postman collection and 20 manual test cases for a public API; month 2, a pytest suite with CI; month 3, a Playwright test and a written test strategy. Add the hours per week you can really give.
Key takeaways
- Roles range from manual QA to automation engineer, SDET and performance tester; read job descriptions for what a title means at that company.
- Build skills in order: testing basics, API tools, one language, pytest or Vitest, mocks and integration, Playwright, CI, then load and security basics.
- Evidence beats keywords: a small GitHub portfolio with CI, a README and your own explanations.
- Practise interview basics: severity versus priority, HTTP status codes, what to automate, flaky tests and a short coding round.
- Certifications such as ISTQB CTFL can help freshers, but check the official page for the current details and don't treat them as a replacement for projects.
- Principles outlast tools: risk thinking, clear communication and curiosity.
Check yourself
Finishing the quiz marks the lesson as done.
1. A bug causes a typo in a rarely visited legal page, but the company is launching tomorrow and the page must be correct. How would you describe it?
2. What is the main difference between an automation engineer and an SDET in many companies?
3. Which portfolio item best shows API testing skill?
4. Which is the best thing to automate first?
5. What should you do before paying for an ISTQB exam?
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