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SDET Interview Questions: Your Key to Landing the Job

You can view an SDET (Software Development Engineer in Test) as a more technical version of a manual tester. They write tests, report bugs, and generate reports primarily for automated testing.

The following questions provide a comprehensive overview of the skills and knowledge required for an SDET. Interviewees should be prepared to discuss both high-level concepts and dive into specific technical details, showcasing their versatility and depth of expertise.

SDET Interview Questions

1. Do you think quality assurance and quality control are different? If yes, then how?

Suggested approach: The interviewer will try to assess your understanding of these terms. Try to highlight the differences between the two while also acknowledging that they fall in the same realm.
Sample answer: As per my understanding, quality control and quality assurance differ from one another in the following ways.
Starting with quality assurance it is process-oriented, meaning that the focus remains on the higher-level implementation of quality-related activities. This helps prevent defects by establishing a consistent and efficient process. It is continuous and spans the project’s lifecycle, focusing on process improvements through process mapping, flowcharts, and process auditing.
Now, to quality control, which focuses more on the product and detecting and correcting defects in the finished product. It generally comprises activities such as inspection, testing, and reviews. Quality control typically happens towards the end of the lifecycle when the product is ready for verification.
Read in detail about Quality Assurance vs. Quality Control.

2. How would you differentiate between priority and severity in software testing?

Suggested approach: Tell the difference between the two and how they impact different stakeholders. The latter part will show the interviewer that you are aware of the bigger picture.
Sample answer: Severity refers to the impact of a defect on the system. It describes how severe a bug is, or, in other words, it’s a measure of the defect’s impact on the software’s operation. Priority, however, indicates the urgency with which a defect should be fixed. It is a measure of the business’s importance or the order in which defects should be addressed based on business needs, schedules, or other factors. While severity is about the technical impact of the defect, priority is more about the business or strategic importance of fixing it.
Learn about defect priority vs. defect severity.

3. What is shift-left testing?

Suggested approach: Give the general definition of this approach. You can then add examples of using this approach from your previous experience, if any.
Sample answer: The term “shift-left” signifies moving testing to the “left” or the earlier phases of the project timeline. The primary goal of this approach is to identify and address defects at the earliest possible stage, reducing the cost and effort required to fix them later.
Know more about shift-left testing.

4. What is exploratory testing? Do you think it is a good strategy?

Suggested approach: Talk about what this form of testing entails and then speak on when to use this approach.
Sample answer: This form of testing relies on the tester’s experience, skills, and intuition to identify defects. The tester literally explores the system in hopes of unearthing defects, which then get resolved by the development team. This quick yet unsystematic approach to testing often yields excellent results, but it is not a replacement for systematic testing. In environments like Agile, where changes are frequent and continuous feedback is valuable, exploratory testing can be particularly beneficial. Additionally, it’s helpful in scenarios where there’s limited documentation or the software is too new or changing too rapidly for detailed test scripts to be written.
Read here the QA engineer’s approach to exploratory testing.

5. Explain the software testing lifecycle.

Suggested approach: Mention the stages of STLC and explain them briefly. If you can give examples, then go ahead and add those as well.
Sample answer: STLC is a process followed for testing and comprises the following stages.

  • Requirement Analysis: At this stage, the testing teams evaluate and analyze the requirements from a testing perspective to determine whether the requirements are testable or not. If there are any ambiguities or queries, they are clarified with stakeholders.
  • Test Planning: Here, the test lead or test manager determines effort and cost estimates for the project and outlines how the testing process will proceed. Creation of the test plan document occurs, which includes details about the scope, objectives, resources, testing schedule, and deliverables.
  • Test Design: During this phase, detailed test cases, scripts, and data are created. Testers define the conditions under which the tests will run and identify the expected results. Test data preparation and test case review are also part of this phase.
  • Test Environment Setup: This involves preparing the environment where the testing will take place. It includes setting up the test servers, databases, and any necessary hardware. It’s crucial to ensure the environment mirrors the production environment as closely as possible to avoid environment-specific issues.
  • Test Execution: At this stage, testers begin to execute the test cases. They log defects for any issues they find and link them with the respective test cases. Testers may have to re-execute test cases after defects are fixed to validate the fixes.
  • Defect Reporting and Tracking: If defects or bugs are identified during test execution, they are reported and tracked using defect tracking tools. The status of defects (e.g., open, in-progress, fixed, retested, closed) is monitored until fixed and closed.
  • Test Closure: The testing phase is concluded once testing meets the exit criteria. A test closure report, which summarizes the testing activities and results, is prepared. All the testing artifacts, like test cases, test data, and defect reports, are finalized and archived.

Read in detail about STLC in this guide.

6. What is Agile testing?

Suggested approach: Mention what it is and give its benefits. If possible, state an example as well of the use of this form of testing.
Sample answer: Agile testing is meant for teams using the Agile methodology to build software. Over here, testing happens continuously, often alongside development, allowing for rapid feedback and ensuring that quality is integrated at every step of the process. With Agile testing, one can achieve faster feedback to developers, early detection and resolution of defects, better collaboration between developers, testers, and stakeholders, higher customer satisfaction due to the delivery of more relevant features, and consistent quality.
This is a good article about the roadmap to better Agile testing.

7. What are some challenges you’ve faced when testing in different browsers or platforms?

Suggested approach: The interviewer wants to know your experience and familiarity with mobile testing through this question. You can mention some challenges as well as solutions that you came up with to tackle those challenges.
Sample answer: Some of the challenges that I have faced are

  • Improper rendering of UI
  • Difficulty in reusing the same test script across different platforms
  • Flakey test runs on different platforms due to changes in the position of elements

As a solution, it is better to choose an automation testing tool such as testRigor that can handle mobile testing and even make the process easier.
Read this article to learn how to start mobile testing.

8. What is your take on sacrificing the testing scope to meet delivery deadlines?

Suggested approach: This is a tricky question where the interviewer wants to gauge how well you prioritize and balance testing activities with business commitments.
Sample answer: In this Agile delivery mode, it is an open secret that the time-to-market always falls short despite all the planning. I believe in balancing both testing and business commitments over here. Based on the business commitments, it is prudent to invest more time in testing those mission-critical areas and then, if time permits, move on to the other sections. Leveraging automation test suites for regression testing tends to help most of the time.

9. How do you ensure that your automated tests are maintainable and easy to understand for other team members?

Suggested Approach: Talk about how you keep the code base clean while ensuring that others follow what you’ve written.
Sample answer: I believe writing test scripts is similar to writing application code. Hence, I tend to adhere to a consistent coding standard and use descriptive naming for tests, variables, and methods. As helpful as comments are, using them judiciously is likely to be more effective as a good piece of code is self-explanatory. Further, I am clear with what I am testing and write focused test cases while organizing tests into suites or categories based on their functionality or the features they test. Through data-driven testing or external configuration files to separate test data from the test logic, I find it easier to manipulate and maintain test cases. Finally, tests should be regularly refactored to make them lighter and updated.

10. How do you stay organized with multiple projects and deadlines?

Suggested approach: Let the interviewer know that you are organized and systematic in your work. You can do this through examples as well.
Sample answer: Prioritizing my tasks and preparing a personal action plan helps me meet deadlines. I consider the testing scope of each project, the deadlines associated with each, the business criticality of these projects, and the available bandwidth to prepare a solid action plan.

11. How do you stay updated with industry trends?

Suggested approach: Talk about different ways in which you keep track of industry trends and also mention examples for the same. This will help the interviewer know that you are curious about the industry and want to keep learning.
Sample answer: I have subscribed to various new letters and magazines for this purpose. Along with that, I enroll in seminars and courses and participate in any workshops that are arranged in the workplace for this purpose. Keeping in touch with peers in the industry has also helped me stay up-to-date about the trends and practices being followed across the board.

12. How would you go about creating an automation strategy for a product that doesn’t have any automation tests?

Suggested approach: Show the interviewer that you are systematic and analytical when it comes to designing strategies. Explain how you will evaluate the present situation of the product and then devise ways to make it better. If you’ve implemented this sort of strategy before, then explain that as well.
Sample answer: In this case, I would first see what testing is being done for the product. This will help me get an idea of the testing scope as well as any manual test cases that are being used. Then, I will create module-wise test suites from which I will create a smoke test suite, sanity test suite, and regression test suite. These suites can run after every release. Once I am done bridging this delta, I will add test cases for new functionality to these suites and start working on a performance testing suite.
You can read more about this over here.

13. How do you decide which tests to automate and which ones to run manually?

Suggested approach: Both manual and automated tests have their pros and cons. Use this opportunity to showcase that you understand this and try to leverage the pros of both manual and automated testing.
Sample answer: I believe in leveraging both manual and automated testing as they both have their advantages and disadvantages. Through automation testing, I try to cover a more extensive scope and all the repetitive testing tasks like smoke testing, regression testing, sanity testing, or other forms of functional or non-functional testing in every cycle. I save manual testing for those tasks that require mandatory human intervention, like testing new features through exploratory testing or UI/UX testing.
Here is a detailed article on which tests I should automate first.

14. Describe a time when you disagreed with a developer about a bug. How did you handle it?

Suggested approach: The interviewer is gauging your communication and conflict management skills. These are important when one has to work in a team.
Sample answer: This happens quite often, especially in high-pressure projects. During such times, I keep my calm and put facts on the table to explain my point. For example, if I observe a functional bug the developer disagrees with, I pull up the documented requirement to cross-reference the expectation. If that doesn’t solve the problem, then we approach the product owner and the project lead to get a clear understanding. Throughout this exercise, I try to remind both of us that we are on the same team and should focus on satisfying the customer.

15. How do you measure the effectiveness or coverage of your tests?

Suggested approach: Explain different metrics or strategies that you use to assess this. You can use examples here as well.
Sample response: There are a couple of ways I do this. The first is through requirement tracking to see corresponding test cases. I use JIRA and TestRail for this. Next, I look at the defects being raised. A couple of details can be learned from here. A higher defect density in an area might indicate insufficient or ineffective testing. Likewise, a higher rate may indicate issues in the testing process or areas that might have been overlooked. Even with automated tests, exploratory testing can uncover problems that structured tests miss. Along with load testing, performance testing helps identify and fix those bottlenecks. Finally, boundary and edge case testing also help keep the quality control under check.
You can read more about project-related metrics here.

16. How do you ensure that your test data is both comprehensive and relevant?

Suggested Approach: Use this question to show the interviewer that you are thorough with your research and look up ways to improve the quality of your test cases.
Sample answer: The production data is the primary reference source for creating test data. I prefer to study this data, speak to developers about commonly encountered data values, and read up on historical data about bugs logged, as they also point out some edge cases of data types. After all this, I then proceed to create my test data for the test suite. While doing so, I never hard code; instead, I use a test-driven approach.
Read about Test Driven Development (TDD).

17. As an SDET, what is your understanding of CI/CD?

Suggested approach: CI/CD is an important concept used widely in most companies. Read up on how SDETs integrate with it and ensure better quality control. SDETs write and maintain the automated tests that serve as the safety net for this process, ensuring that releases maintain a high quality. Explain this to the interviewer to show that you know these practices. If you’ve used them before, then feel free to add examples.
Sample answer: Continuous Integration (CI) emphasizes integrating code changes frequently, often multiple times daily. These integrations can introduce defects. An SDET ensures that automated tests are executed as part of the CI process to validate every code change, catching issues early. They do this by configuring the CI/CD pipeline to provide rapid feedback to developers. If a test fails, developers are immediately notified, allowing for quick resolutions. For an SDET, CI/CD transforms the traditional siloed approach to development and testing into a collaborative and continuous process. The emphasis shifts from finding defects after the fact to preventing them in the first place and ensuring a consistently high-quality software release process.
See two good blogs about TestOps and DevTestOps.

18. What is your understanding of a test plan? Do you think it’s worthwhile?

Suggested approach: A test plan is crucial for systematic testing. Let the interviewer know that you understand its importance and mention some of its components. Do add examples of how it has helped you.
Sample answer: A test plan acts as a guideline for us SDETs, thus making it very important. We use it to learn about the scope of testing, types of testing that need to be performed, responsibilities of team members, sprint schedules, deadlines, business objectives, testing objectives, and more.
Here is a complete guide on test planning.

19. Do SDETs need to worry about non-functional requirements? Why and what should they do about them?

Suggested Approach: Talk about the importance of non-functional requirements and a few of their different types. If possible, add examples.
Sample answer: While functional requirements specify what a system is supposed to do, non-functional requirements specify how the system should behave. This can be checked through performance tests, security tests, usability tests, scalability tests, disaster recovery testing, compliance testing, and more. SDETs play a crucial role in ensuring that software not only works as intended but also meets the standards of performance, security, usability, and other non-functional criteria.
Learn in detail the differences between functional and non-functional testing.

20. What do you think are the roles and responsibilities of an SDET?

Suggested approach: Explain your understanding of this role. If you have work experience, then you can add examples. However, remember that in the Agile environment, no role is a silo role, and hence, think holistically when stating points.
Sample answer: An SDET has the task of creating and maintaining automated testing on different platforms, has knowledge about deployment to work with CI/CD, Confident communicator to handle discussions with stakeholders to gain further understanding of requirements, sound technical knowledge to hold conversations with developers to understand bug fixes, good learner to understand the product, and a team player.

Coding-related questions

You may be asked some coding problems where you must write the logic to showcase that you are well-versed in your basics. Some examples of such questions are mentioned below.

  • Write a function to determine if a string has all unique characters.
  • Given two sorted arrays, write a method to merge them into a single sorted array.
  • Describe and code an algorithm to find the first non-repeated character in a string.
  • How would you test a binary search tree?
  • Implement a basic regular expression parser that can handle “.” (any character) and “*” (zero or more of the preceding character).
  • Switch two numbers without using a third variable.
  • Generate a Fibonacci series.

System design questions

These questions are meant to test your logical thinking by applying them to a real-life problem statement. Some sample questions in this category could look like this.

  • How would you design a logging system to capture and report errors for a large-scale web application?
  • If you were to design an end-to-end testing framework for a microservices architecture, what would be its key components?

Summing it up

This list gives a mix of technical, situational, and theoretical questions that are often posed to SDET candidates during interviews. As always, thorough preparation and understanding of the underlying principles behind each question will be beneficial.

For the interview, prepare for questions that are theoretical and conceptual, technical and coding-related, scenario-based, related to system design, tools, and environment-related (What software testing tools did you use in your previous SDET position?), or related to the candidate’s behavior or situations.

Remember to be confident when answering questions, and don’t shy away from sharing examples from your experience. For freshers, use this opportunity to study more about this role and speak to experienced peers in the industry who have been in this role.

Useful links for further reading

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