What is the difference between black box and white box testing?

 Theme: Software Testing Techniques  Role: Qa Engineer/Test Engineer  Function: Technology

  Interview Question for QA Engineer/Test Engineer:  See sample answers, motivations & red flags for this common interview question. About QA Engineer/Test Engineer: Ensure software quality through testing and quality assurance. This role falls within the Technology function of a firm. See other interview questions & further information for this role here

 Sample Answer 


  Example response for question delving into Software Testing Techniques with the key points that need to be covered in an effective response. Customize this to your own experience with concrete examples and evidence

  •  Definition of black box testing: Black box testing is a software testing technique where the internal structure, design, and implementation details of the system under test are not known to the tester. The focus is on testing the functionality and behavior of the system
  •  Key characteristics of black box testing: 1. Testers have no knowledge of the internal workings of the system. 2. Test cases are derived from the system's requirements and specifications. 3. It is primarily focused on validating the system's functionality and user experience. 4. Testers simulate real-world scenarios to identify defects or deviations from expected behavior
  •  Advantages of black box testing: 1. Testers do not require programming knowledge or access to the source code. 2. It ensures that the system meets the specified requirements and behaves as expected from the end-user's perspective. 3. It helps in identifying issues related to usability, functionality, and compatibility. 4. It allows for independent testing, as the testers can focus solely on the system's behavior without being influenced by its internal implementation
  •  Limitations of black box testing: 1. It may not uncover all possible defects, as it relies on predefined test cases. 2. It can be time-consuming to create comprehensive test cases covering all possible scenarios. 3. It may not be suitable for testing complex algorithms or performance-related issues. 4. It may not provide insights into the root cause of defects, making debugging and fixing more challenging
  •  Definition of white box testing: White box testing, also known as clear box or glass box testing, is a software testing technique where the tester has full knowledge of the internal structure, design, and implementation details of the system under test. The focus is on testing the internal logic, code coverage, and structure of the system
  •  Key characteristics of white box testing: 1. Testers have access to the source code and can analyze it for testing purposes. 2. Test cases are derived from the internal structure and implementation details of the system. 3. It aims to ensure the correctness of the system's internal logic and code. 4. It helps in achieving high code coverage and identifying potential vulnerabilities or weaknesses in the system
  •  Advantages of white box testing: 1. Testers can design test cases based on the internal structure, allowing for thorough testing. 2. It helps in identifying issues related to code quality, security vulnerabilities, and performance bottlenecks. 3. It allows for early detection of defects, as testing can be performed during the development phase. 4. It provides insights into the root cause of defects, making debugging and fixing easier
  •  Limitations of white box testing: 1. Testers require programming knowledge and access to the source code, which may not always be feasible. 2. It may not uncover defects related to system integration or external dependencies. 3. It can be time-consuming to analyze and test the internal structure of complex systems. 4. It may not fully validate the system's behavior from an end-user's perspective

 Underlying Motivations 


  What the Interviewer is trying to find out about you and your experiences through this question

  •  Knowledge & understanding of testing methodologies: Assessing the candidate's understanding of black box and white box testing and their ability to explain the differences
  •  Experience & expertise in testing: Determining the candidate's level of experience and expertise in different testing techniques
  •  Problem-solving skills: Evaluating the candidate's ability to apply the appropriate testing approach based on the given scenario
  •  Attention to detail: Assessing the candidate's attention to detail in identifying and testing different components of a system

 Potential Minefields 


  How to avoid some common minefields when answering this question in order to not raise any red flags

  •  Lack of understanding: Providing incorrect or vague definitions of black box and white box testing
  •  Inability to differentiate: Not being able to clearly explain the differences between black box and white box testing
  •  Limited knowledge: Showing a lack of knowledge about the advantages, disadvantages, and use cases of black box and white box testing
  •  Inflexibility: Failing to acknowledge that both black box and white box testing have their place in the testing process and dismissing one over the other
  •  Lack of experience: Not being able to provide real-world examples or experiences related to black box and white box testing

 Related

  Other questions asked for the QA Engineer/Test Engineer in Technology function. View details for the QA Engineer/Test Engineer here