39 Unit Testing Interview Questions (With Sample Answers)

July 9, 2021

Unit testing assesses the code for software technologies and is common in the computer science career field, so preparing for an interview in this profession is important. Typically, these interviews include industry-specific questions to test the expertise and knowledge of candidates. If you're preparing to interview for a unit testing position, consider practicing your responses to potential interview questions ahead of time. In this article, we discuss interview questions to expect during a unit testing interview and provide 10 examples of questions with sample answers.

General questions

General interview questions may help interviewers get to know you on a more personable level and encourage conversation. These may also help prepare you for qualification questions later on in your interview. Here are some example questions they might ask at the beginning of your interview:

  • How did you first learn about this position?
  • What interested you in applying?
  • Why do you want to work for our company?
  • Share a little about yourself.
  • If you had to pick three adjectives to describe yourself, what would they be and why?
  • What do you believe your strengths are, and what do you believe your weaknesses are?
  • Do you prefer working individually or with a team?
  • Tell us about your professional goals.
  • After reviewing the job description, do you have questions about the position?
  • Do you have questions about our company?

Related: 125 Common Interview Questions and Answers (With Tips)

Questions about experience and background

Interviewers may ask questions about your professional experience and background to help them understand your knowledge and relevant qualifications for the job. Here are some example questions that might help you prepare:

  • Tell us about your educational background.
  • Have you engaged in professional unit testing training?
  • Do you have any relevant certifications or licensure?
  • Are you interested in continuing to learn and grow your skill sets?
  • How many years of experience do you have working with software technologies?
  • What first interested you in unit testing?
  • Tell us about your previous positions in the same or similar roles, including daily duties.
  • Do you have experience in leadership roles? If so, how would you describe your leadership style?
  • Tell us about the skill sets you have gained from your educational and professional experiences.

In-depth unit testing questions

Interviewers may ask in-depth questions to learn more about your specific knowledge regarding unit testing for software technology programs. Here are some example questions you might expect during your interview:

  • Describe the different unit testing types you might use for software applications.
  • What is your approach, strategy or method for designing a strong unit testing case? Provide examples if applicable.
  • Tell us about different code coverage techniques and how you might use each of them.
  • What best practices do you use when conducting unit testing?
  • Share with us your experience using unit testing frameworks, including which you have used and how you have used them.
  • What do you know about interaction-based unit testing?
  • Tell us about what you typically include in a unit testing brief.
  • Throughout your previous experiences, how has unit testing provided benefits?
  • How many phases of unit testing do you usually use?
  • What are some unit testing tools or resources you have previously used?

Related: 12 Tough Interview Questions and Answers

Interview questions with sample answers

Here are 10 unit testing interview questions with sample answers to help guide your interview preparation:

1. Can you describe your understanding of unit testing case phases?

This question is asked to test your knowledge about the process of unit testing throughout each standard case phase. The interviewer may request that you showcase your knowledge and provide specifics when answering this question. When considering your response, think about the training you've had in order to be concise and efficient during the interview.

Example: "Unit testing cases typically include three standard phases. The first phase focuses on setting the values and conditions for the specific software application that you will test. The second phase is when the actual testing of the software happens and the third phase is where you can analyze the outcome and test results. In my previous experiences, I have used these phases often as guides when conducting software application unit testing processes."

2. What are the differences between acceptance and functional testing?

This question may allow you to share your knowledge of the differences between different unit tests. Consider how you would explain the differences, such as steps and phases for each. Try providing as much information during this time to highlight your knowledge of the two testing types.

Example: "Acceptance and functional testing have two different purposes in relation to unit testing. Acceptance testing focuses on validation to ensure the software actually solves the problem programmers developed it to address. Meanwhile, functional testing focuses on verifying if the software is meeting company requirements and functions efficiently. I have used both testing methods in the past at different stages of the unit testing process."

3. What is the purpose of mocking in relation to unit testing?

Interviewers may ask this question to allow you an opportunity to showcase your industry vocabulary and functional knowledge. You might use your background and understanding to provide general descriptions and your previous professional experiences to provide specific examples. Try staying on topic when discussing specifics about the purpose of this unit testing.

Example: "Mocking is a common method and strategy used in unit testing because it helps with the observation process of examining software code structures and behaviors. When I have used mocking in the past, it has helped me to separate object behaviors and replace them with objects that function in similar ways. Essentially, allowing me to produce objects that simulate the same observed behaviors as actual objects. I have found this is beneficial for identifying software dependencies."

4. What percentage of code coverage do you think is appropriate for unit testing? Why did you choose this percentage?

The interviewer or interviewing committee may ask this question to assess your decision-making skills in relation to unit-testing best practices. Since this is a two-part question, consider providing a two-part answer. Doing so allows you the opportunity to provide clear and concise answers to both questions, while also providing an additional opportunity to showcase your analytical skills.

Example: "The percentage of code coverage I might choose may vary on the software I am unit testing. Although, if I had to choose a general percentage, I would say 75% because this percentage still allows for code assessment without slowing down the unit testing process. Sometimes I also use functionality coverage during unit testing, to ensure that the code I am testing maintains its behaviors."

5. Are you familiar with white box testing and have you used it in your previous professional experiences?

Interviewers may ask this question to test your expertise regarding a specific testing type. When answering direct questions such as this, consider your competency level and answer as truthfully as you can. If you only used the type a few times in past professional experiences, try explaining when, how and why you did.

Example: "Yes, I have used white box testing in my previous professional experiences. Specifically, I used it to help me identify potential internal security weaknesses within the software I was unit testing and to evaluate how the code responded to different input values. Although this sometimes took longer, I found it helpful to ensure the software was ready for use after unit testing."

Read more: What Is White Box Testing?

6. Describe the differences between unit, integration, smoke and regression testing for software.

The interviewer might ask you this question to test your knowledge about different software testing types. Try providing obvious differences and specific information regarding each type. Consider following the question's pattern in order to stay on track.

Example: "Each of these tests has a different purpose in relation to testing software technologies. You use unit testing to narrow the focus to specific points of interaction. Meanwhile, interaction testing can examine internal interactions and functionalities within software technologies. Smoke testing is useful for ensuring software systems function correctly and don't stop working while in use. Finally, you might use regression testing after removing a bug from a software system to ensure the new code functions properly. My primary experience is with unit testing, but I have conducted interaction and smoke testing as well in my previous work."

Related: The Phases of Software Testing: Explanation and Steps

7. Are you familiar with frameworks related to unit testing? If so, which ones have you used?

This question may provide you with an opportunity to share your knowledge of frameworks related to the duties required by the position. Try explaining your general and advanced knowledge with your answer. It might be helpful to give examples of a few frameworks you're familiar with and how you used them daily.

Example: "I am familiar with frameworks related to unit testing. Throughout my previous professional experiences, I have used C# and JavaScript unit testing frameworks. I am proficient in using both frameworks and, if chosen, would apply my working knowledge of them to this position."

8. If you haven't used the JUnit framework for unit testing, do you know what it is and how it works?

The interviewer may ask this question to gain more insight into your background knowledge of unit testing frameworks. If you haven't used a particular framework but are familiar with it, inform the interviewer and consider following up with a reason for not doing so or an interest in working with it in the future. As you may have common knowledge of this framework, explaining this to the interviewer may help in the decision process.

Example: "Although I haven't used the JUnit framework for unit testing, I am aware of what it is and understand the benefits it can provide for regression testing. If I needed to increase program speed or the code quality, I might consider using this framework."

9. Describe a challenging experience with unit testing. How did you resolve it?

The interviewer might ask this question to learn more about how you approach challenges and the level of your problem-solving skills. For this question, you may specifically want to share an example of a challenge you resolved during your previous professional experiences with unit testing. Consider providing a challenge that you can explain thoroughly and concisely.

Example: "A challenging situation I previously encountered was during a project where I had to use a coding language that I hadn't learned. At first, I was concerned and knew that I didn't want to miss something in testing. So, I taught myself the basics of the coding language so I better understood it as I conducted the unit testing. Although this required more of my time, it allowed me to conduct unit testing more efficiently."

10. If selected for this position, how might you apply your relevant skill sets?

This question might help your interviewer or the interviewing committee better understand how you might use your skill sets in the position. Crafting an answer that clearly highlights your abilities and the potential benefits they offer may help you be more noticeable. For this question, you may highlight relevant skills specific to working with technology and codes.

Example: "I know my skill sets in coding languages, organization, documentation, customer support and project management will help me excel in this position if I am selected. My coding language skill set can provide benefits for understanding the different software I might test. My organization and documentation skill sets may also provide benefits in this position because I will be able to effectively and efficiently record and analyze testing results. Also, my customer support and project management skill sets may provide benefits by allowing me to problem-solve with unit-testing best practices."


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