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Software Development Engineer in Test (SDET) is a crucial role in the tech industry, blending software development and quality assurance expertise. If you’re preparing for an SDET interview, you need to master coding, automation, testing methodologies, and system design.

This guide covers 50+ SDET interview questions and answers, categorized for easy learning. Whether you’re a beginner or an experienced professional, these questions will help you ace your interview.

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SDET Interview Questions and Answers

1. Basic SDET Interview Questions

Q1. What is an SDET?

Answer: An SDET (Software Development Engineer in Test) is a professional who develops automated testing frameworks and tools to ensure software quality. They write code to test applications and work closely with developers to improve test coverage.

Q2. What’s the difference between SDET and QA Engineer?

Answer:

• SDET writes code to automate tests, builds testing frameworks, and works on testability improvements.
• QA Engineer focuses on manual testing, test case design, and execution but may not necessarily code.

Q3. What programming languages should an SDET know?

Answer:

• Java (Most common in automation)
• Python (Easy syntax, great for scripting)
• C# (Used in .NET applications)
• JavaScript (For front-end and Node.js testing)

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2. Automation Testing Interview Questions

Q4. What is Selenium? Why is it used?

Answer:
Selenium is an open-source automation tool for web applications. It supports multiple browsers and programming languages.

• Selenium WebDriver allows direct browser control.
• Selenium Grid enables parallel test execution.

Q5. Explain the difference between Selenium RC and WebDriver.

Answer:

Feature	Selenium RC	Selenium WebDriver
Architecture	Uses JavaScript	Direct browser interaction
Speed	Slower	Faster
Browser Support	Limited	Wider support

Q6. How do you handle dynamic elements in Selenium?

Answer:

• XPath/CSS Selectors: Use relative XPath (//div[@class='dynamic-class']).
• Explicit Waits: WebDriverWait to wait for elements.
• Dynamic IDs: Use partial attribute matching (contains, starts-with).

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3. Coding & Algorithm Questions for SDET

Q7. Write a code to reverse a string in Java.

Answer:

public String reverseString(String str) {  
    return new StringBuilder(str).reverse().toString();  
}  

Q8. How do you find duplicates in an array?

Answer:

public List<Integer> findDuplicates(int[] nums) {  
    List<Integer> duplicates = new ArrayList<>();  
    Set<Integer> set = new HashSet<>();  
    for (int num : nums) {  
        if (set.contains(num)) duplicates.add(num);  
        else set.add(num);  
    }  
    return duplicates;  
}  

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4. Testing & Framework Questions

Q9. What is TestNG? Why use it over JUnit?

Answer:
TestNG is a testing framework with advanced features:

• Annotations (@BeforeTest, @DataProvider)
• Parallel execution
• HTML reports
• Parameterized testing

Q10. Explain the Page Object Model (POM).

Answer:
POM is a design pattern where:

• Each web page is represented as a class.
• Locators and methods are stored in the class.
• Improves maintainability and reduces code duplication.

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5. Performance & API Testing Questions

Q11. What is API testing? How do you automate it?

Answer:
API testing validates backend services using tools like:

• Postman (Manual testing)
• RestAssured (Java-based automation)
• JMeter (Performance + API testing)

Q12. How do you measure performance of an API?

Answer:

• Response Time (Time taken for a request-response cycle)
• Throughput (Requests per second)
• Error Rate (Percentage of failed requests)

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People Also Ask (FAQs)

1. What is the salary of an SDET?

• Entry-level: 70K–70K–90K
• Mid-level: 90K–90K–120K
• Senior-level: 120K–120K–160K+

2. Is SDET a good career choice?

Yes! SDETs are in high demand due to the rise in automation testing and CI/CD pipelines.

3. What skills do I need to become an SDET?

• Programming (Java/Python)
• Automation Tools (Selenium, TestNG)
• CI/CD (Jenkins, Docker)
• Performance Testing (JMeter, Gatling)

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Conclusion

Preparing for an SDET interview requires a mix of coding, automation, and testing knowledge. This guide covered 50+ SDET interview questions and answers to help you succeed.

Pro Tip: Practice coding problems, automate test cases, and understand system design to stand out.

🚀 Ready to ace your SDET interview? Bookmark this guide and start practicing today!