SDET interview prep

What the job involves

SDETs at global tech companies design, build, and maintain automated test frameworks and tools that validate software at scale. They work closely with developers and product teams to ensure quality is baked into the development lifecycle, often writing code to test APIs, UIs, and backend services. The role blends software engineering with testing, requiring strong coding skills and a quality-first mindset.

Role and Technical Knowledge

1. 1

   What is the difference between a test case, a test suite, and a test plan?

   A strong answer defines each clearly and explains how they relate hierarchically, with examples from a simple login feature.

2. 2

   How would you test a REST API endpoint that returns a list of orders for a user?

   Cover status codes, response schema, authentication, pagination, error cases, and data validation against the database.

3. 3

   Explain the Page Object Model and why it is useful in Selenium automation.

   Highlight code reusability, maintainability, and separation of test logic from page locators, with a brief example.

4. 4

   What are the key differences between smoke, sanity, and regression testing?

   Define each type, when they are run, and how they fit into a release cycle, using a checkout flow as an example.

Practical Scenarios and Coding

1. 5

   Write a function to find the first non-repeating character in a string. How would you test it?

   Provide an efficient solution (e.g., using a hash map) and list edge cases like empty string, all repeating, and special characters.

2. 6

   You have a flaky test that passes 80% of the time. How do you debug and fix it?

   Discuss isolating the cause (timing, environment, test data), adding waits, logging, and making tests deterministic.

3. 7

   How would you automate testing of a login page with username, password, and a CAPTCHA?

   Explain handling CAPTCHA via test environment bypass, using data-driven tests for valid/invalid inputs, and asserting error messages.

4. 8

   Given a database table of users, write a SQL query to find users who signed up but never placed an order.

   Use a LEFT JOIN or NOT EXISTS with a subquery, and explain how you would verify the result in a test.

Behavioural and HR

1. 9

   Tell me about a time you found a critical bug late in a project. What did you do?

   Use STAR format: describe the situation, your action to assess impact and communicate, and the outcome including preventive measures.

2. 10

   How do you handle disagreements with a developer who says a bug is not reproducible?

   Show collaboration: gather detailed logs, reproduce together, and focus on user impact rather than blame.

3. 11

   Why do you want to be an SDET rather than a pure developer or manual tester?

   Connect your interest in coding with quality ownership, and mention building tools that scale testing efforts.

4. 12

   Describe a situation where you had to learn a new testing tool quickly for a project.

   Highlight self-learning, resourcefulness, and how you applied the tool to deliver results under time pressure.

Automation Frameworks and Tools

1. 13

   What are the advantages of using a data-driven framework over a linear test script?

   Discuss reusability with external data sources, easier maintenance, and broader coverage with fewer scripts.

2. 14

   How do you integrate automated tests into a CI/CD pipeline?

   Explain triggering tests on code commits, using Jenkins/GitHub Actions, reporting results, and gating deployments on test success.

3. 15

   What is the role of Maven or Gradle in a Selenium project?

   Cover dependency management, build lifecycle, and running tests via command line, with a simple pom.xml example.

4. 16

   How would you test a microservices-based application where services communicate asynchronously?

   Mention contract testing, mocking dependencies, verifying eventual consistency, and monitoring logs for failures.