15 Debugging Interview Questions and Answers

Debugging is a process of finding and resolving defects or problems within a computer program that prevent it from running correctly. Debugging can be done manually or with the help of specialized tools.

When interviewing candidates for a position that will involve debugging, it’s important to ask questions that will give you insight into their problem-solving skills and ability to think critically. Here are some sample debugging interview questions and answers that can help you find the right candidate for the job.

1. What is the purpose of debugging?

Debugging is a process that allows developers to identify and fix errors in software. This question helps the interviewer assess your debugging skills by asking you to explain what they are and how they help you complete projects. Use examples from previous experiences where you used debugging to solve problems or improve existing code.

Example: “Debugging is an essential part of my job because it allows me to find and correct errors in code before I release it. In my last role, I was working on a project when I noticed some issues with the coding. I started debugging the program to see if I could locate the problem. After several hours of testing, I found that there were multiple bugs in the code. I fixed these issues and released the final product.”

2. What are some tools that you commonly use for debugging code?

Debugging code requires a variety of tools to ensure the code is working properly. The interviewer may ask this question to see if you have experience using debugging tools and which ones you prefer. List some common tools that you use for debugging code, such as:

Example: “I usually use a debugger like Visual Studio or NetBeans IDE because they allow me to step through code line by line and watch variables change in real time. I also use a profiler tool to determine where my code is running slowly. Finally, I use a unit testing framework to test individual units of code so I can make sure it’s functioning correctly.”

3. How do you debug a python program on Linux?

Debugging is a skill that requires you to use your knowledge of programming languages and operating systems. This question allows the interviewer to assess how well you know Linux, as it’s one of the most common operating systems used in software development. In your answer, demonstrate your ability to adapt to different environments by providing an example of debugging on another operating system.

Example: “I have experience working with Python on Windows, so I would first check if there are any bugs in my code using pdb.set_trace(). Then, I’d run the program using pythonw.exe -i .py. Next, I’d set up ipdb as the debugger by running ipdb.ipdb() from the command line. Finally, I’d enter ‘c’ to continue execution until the next breakpoint.”

4. How do you debug a java program?

This question is a great way to test your debugging skills. It allows you to show the interviewer how you apply your knowledge of java and debug programs. You can answer this question by explaining what steps you take when debugging a java program.

Example: “I start by identifying the problem in the code, which I do by reading through it carefully. Then, I set breakpoints at certain points in the code where I think there may be an issue. After that, I run the program until it reaches one of the breakpoints. At this point, I step through each line of code to see if I notice any issues. If I find something wrong with the code, I fix it and then continue running the program until it reaches another breakpoint.”

5. How would you go about debugging a Java application deployed to Tomcat running in Docker?

This question is a great way to test your debugging skills and knowledge of specific applications. You can answer this question by describing the steps you would take to debug the application, including any tools or resources you might use along the way.

Example: “I would first check if there are any errors in the logs. If I find an error, I will then look at the stack trace for more information about what caused the error. Next, I will set up my IDE to connect with the Docker container running Tomcat. Then, I will run the Java debugger on the deployed application. After that, I will step through each line of code until I find the problem.”

6. What’s the difference between bug and defect?

This question tests your knowledge of the terminology used in software development. It also helps you show that you can apply what you know to real-world situations. Your answer should include a clear definition for each term and an example of when you’ve used them in your work.

Example: “A bug is a problem with the code, while a defect is a problem with the product. For instance, if I was working on a website’s search function and it didn’t return any results, this would be a defect. If I found out that there were no keywords entered into the search box, then this would be a bug.”

7. What is the best way to handle bugs discovered after release?

Debugging is a process that can be challenging, especially when bugs are discovered after release. Your answer should show the interviewer you know how to handle this situation and ensure your work meets quality standards.

Example: “I always try to find out why a bug was missed during testing. I then fix it as soon as possible so it doesn’t affect users. If there’s no way to avoid releasing with the bug, I make sure to include instructions on how to resolve it in case anyone encounters it. This helps prevent customer dissatisfaction.”

8. Can you explain how to debug an issue with a web service call?

This question is a great way to test your debugging skills and knowledge of web services. It also shows the interviewer that you have experience working with complex issues in an IT environment.

Example: “When debugging a web service call, I first check for any syntax errors or missing parameters. If there are no syntax errors, then I check if the client has provided valid credentials. After checking these two things, I will look at the server side to see if it’s responding correctly. If all three checks come back negative, then I know that the issue lies within the network connection.”

9. What happens when you execute a program without compiling it first?

This question is a great way to test your debugging skills. It also allows you to show the interviewer that you know how to use the compiler and other tools in the development environment.

Example: “When you execute a program without compiling it first, you are essentially running the code as plain text. This means that any bugs or errors will be displayed on screen for everyone to see. If I’m working with a client who wants their programs to run smoothly, I’ll always compile them before executing them. Compiling the program ensures that all of the code is correct and ready to run.”

10. Can you explain what a stack trace is?

Stack traces are a common debugging tool that many developers use. Your answer should show the interviewer that you know how to use stack traces and can explain them in simple terms.

Example: “A stack trace is a list of all the functions that were called when an error occurred. It shows where the error started, which function was executing at the time and what line of code it was on. Stack traces are very useful for finding bugs because they allow me to see exactly where the problem occurred.”

11. How can you debug an infinite loop?

Debugging an infinite loop is a common task for programmers. Your answer should show the interviewer that you know how to debug this problem and can apply your knowledge of programming languages to solve it.

Example: “The first step in debugging an infinite loop is identifying which part of the code is causing the loop. Once I’ve identified the section, I’ll check if there are any loops within the main loop. If not, then I’ll look at the conditions under which the loop starts and ends. If the conditions are correct, then I’ll need to find out why the loop never ends. This could be because of a missing break statement or a bug in the logic.”

12. Why does debugger output vary from compiler to compiler?

Debugger output can vary from compiler to compiler because of the different ways each one processes code. This question tests your knowledge about debugging and how it relates to other programming concepts. In your answer, explain why debugger output varies between compilers and what you would do in this situation.

Example: “Debugger output differs from compiler to compiler because they use different methods for processing code. For example, some compilers compile code into machine language while others translate it into bytecode. Bytecode is a set of instructions that are interpreted by an interpreter program rather than being executed directly by the computer’s processor. Debuggers like Visual Studio use JIT compilation, which translates code into bytecode so it can be run on the computer.

When I’m working with multiple compilers, I always make sure to check my debugger output after compiling code. If there is no output, then I know the code was successfully compiled. However, if there is output, I compare it to the original source code to see where any differences may have occurred.”

13. If error handling statements are not handled properly, then what would be the impact during runtime?

This question is a continuation of the previous one and tests your knowledge on error handling statements. It also tests how you apply what you know to real-world scenarios.

Example: “If an error handling statement is not handled properly, then it will have no effect during runtime. This means that if there are any errors in the code, they will be ignored by the program and won’t stop execution. If this happens, the application may crash or behave erratically. In some cases, the application may even continue executing without noticing the error.”

14. Do you think that there should be any changes made to existing debugging standards? If so, then can you recommend them?

This question is a great way for an interviewer to assess your critical thinking skills and how you can contribute to the company’s overall success. Your answer should show that you are open to change, but also understand the importance of following existing standards.

Example: “I think it’s important to follow current debugging standards because they help ensure consistency in the quality of code. However, I would like to see more emphasis placed on improving the efficiency of debugging tools so that developers have better access to them. For example, I believe that there should be a standard set of keyboard shortcuts for all debugging tools.”

15. What are some common pitfalls you need to watch out for when debugging a problem?

Debugging is a complex process that requires you to be aware of several pitfalls. The interviewer may ask this question to see if you know how to avoid common mistakes when debugging. Use your answer to highlight your critical thinking and problem-solving skills by explaining the steps you take to ensure you don’t make these errors during a debugging session.

Example: “One pitfall I try to avoid is jumping to conclusions too early in the debugging process. It’s easy to assume what the issue is before you’ve gathered all the information, but it’s important to wait until you have enough data to draw a conclusion. Another pitfall I watch out for is not having a backup plan in case my initial solution doesn’t work. If I’m unsure about how to fix a problem, I’ll do some research or consult with someone who has more experience.”