35 Unit Testing Interview Questions (With Example Answers)

Updated 18 March 2023

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

Unit testing is a process involving methodologies that analyse the code and scripts that constitute software applications and computer programs. Testing engineers scrutinise the code, functionality and utility of applications using a variety of testing methodologies, and this process is integral for ensuring that applications are of high quality. If you are interested in pursuing a role in this domain, you may benefit from reviewing common interview questions and some sample answers. In this article, we examine a list of interview questions for candidates in the field of unit testing and provide sample answers for a few questions.

General Unit Testing Interview Questions

General unit testing interview questions may help interviewers evaluate candidates on a personable level and encourage conversation. Interviewers may ask these questions towards the beginning of an interview to make candidates comfortable and at ease so that they are able to engage in conversation and contribute effectively to discussions that follow. These are some examples of general questions you may encounter in a unit testing interview:

Mention the channel or channels through which you got to know about this vacancy.
Describe your motivations for pursuing a career in this field.
Describe your motivations for pursuing a work opportunity in this particular company.
How would you describe yourself and your work experience?
Use three words to summarise your personality and character.
Are you aware of your strengths and weaknesses? Elaborate.
Do you believe you are capable of working with a team of professionals, or would you rather prefer to work alone?
Briefly outline any career goals you may have.
Have you prepared any questions for us, regarding the job role you are applying for?
Have you prepared any questions for us, regarding the company and the work culture?

Experience-Based Interview Questions

Interviewers may ask questions about your professional experience and background to help them understand more about your knowledge base and your relevant qualifications for the job. These are some examples of interview questions based on experience and education background:

Briefly mention the academic credentials you possess that are relevant for this role.
How many years of experience do you have working with software technologies?
Have you attended any professional training programmes for unit testing?
What licences and certifications do you possess that are relevant to this role?
Do you wish to engage in continuing education and skill development programmes while you work in this role?
How would you rate your experience level, particularly in relation to workflows in the domain of unit testing?
How did you start your career in the field of software development and unit testing?
Briefly outline the duties and responsibilities you had in your previous roles.
Do you possess any administrative experience leading a team of professionals? If so, what style of leadership do you follow?
What competencies have you been able to develop as part of your academic and professional engagements in the past?

In-Depth Interview Questions

Unit testers require specialised knowledge of a variety of aspects of software development. Interviewers ask in-depth questions to gauge the extent of a candidate's expertise and experience working in this field. These are some examples of in-depth interview questions in the field of unit testing:

What are some popular unit testing methodologies that you have experience working with?
Do you follow any particular methods, strategies or approaches for developing efficient and effective testing workflows? If yes, please elaborate.
What are code coverage techniques and how do you typically put them to use?
Are you familiar with industry best practices in the field of unit testing? Can you elaborate on a few that you personally follow?
What established frameworks do you normally use for unit testing and how do you use them?
Describe your experience in unit testing workflows that are interaction-based.
How do you design a brief for a particular unit testing methodology or case?
In your opinion, what are the most pertinent benefits of incorporating unit testing in software development processes?
What is the typical number of phases that exist in a standard unit testing methodology?
Do you use any particular resources or tools for unit testing? If so, please elaborate on the applications and utility of a few of them.

Unit Testing Interview Questions With Sample Answers

These are some common interview questions and sample responses:

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

This question aims to test your knowledge of the process of unit testing throughout each standard case phase. An interviewer may request that you showcase your knowledge and provide specifics while answering this question. While considering a response, think about the training you have had, and be concise during delivery.

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 test. The second phase is when the actual testing of the software happens and the third phase is where you analyse 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 types of unit tests. Consider how you can explain the differences, such as steps and phases for each type. Try providing as much information 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 that the software actually solves the problem programmers have developed it to address. Meanwhile, functional testing focuses on verifying if the software meets 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 in unit testing and it helps with the observation process of examining software code structures and behaviours. When I have used mocking in the past, it has helped me to classify object behaviours and cluster objects that function in similar ways. This essentially enables me to produce objects that simulate the same observed behaviours as actual objects. I have found that this is beneficial for identifying software dependencies.'

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

An 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 behaviours.'

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

An interviewer might ask this question to learn more about how you approach challenges and assess the level of your problem-solving capacity. 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 detailing 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 had not learned. At first, I was concerned and knew that I did not want to miss something in testing. I taught myself the basics of the coding language so that I understood it better as I conducted the unit testing. Although this required more of my time, it allowed me to conduct unit testing more efficiently.'