Interview questions on Software Testing

1. What is PDCA cycle and where testing fits in? Software testing is an important part of the software development process. In normal software development, there are four important steps, in short, the PDCA (Plan, Do, Check, Act) cycle.  Plan: Define the goal and the plan for achieving that goal.  Do/Execute: Depending on the plan strategy decided during the plan stage we do execution accordingly in this phase.  Check: Check/Test to ensure that we are moving according to plan and we are getting the desired results.  Act: During the check cycle, if any issues are there, then we take appropriate action accordingly and revise our plan. Developers and other stakeholders of the project do the "planning and building," while testers do the check part of the cycle. Therefore, software testing is done in check part of the PDCA cycle. 2. What is usability testing? Usability testing is a testing methodology where the end customer is asked to use the software to see if the product is easy to use, to see the customer's perception and the amount of time taken to use the software for a task. The best way to finalize the customer point of view for usability is by using prototype software during the initial stages. This way we can confirm that we are not missing anything from the user point of view. 3. Which is the best testing model? In real projects, tailored models are proven to be the best, because they share features from The Waterfall, Iterative, Evolutionary models, etc. and can fit into real life time projects. Tailored models are most productive and beneficial for many organizations. If it's a pure testing project, then the V model is the best. 4. What is the difference between a defect and a failure? When a defect reaches the end customer it is called a failure and if the defect is detected internally and resolved it's called a defect. 5. Should testing be done only after the build and execution phases are complete? In traditional testing methodology testing is always done after the build and execution phases. Fixing a defect in maintenance is ten times costlier than fixing it during execution. So the earlier we catch a defect the more cost effective it is. In the requirement phase we can verify if the requirements are met according to the customer needs. During design we can check whether the design documents cover all the requirements. In this stage we can also generate rough functional data. We can also review the design document from the architecture and the correctness perspectives. In the build and execution phase we can execute unit test cases and generate structural and functional data. And finally comes the testing phase, done in the traditional way i.e. run the system test cases and see if the system works according to the requirements. During installation we need to see if the hardware system is compatible with the software. Finally, during the maintenance phase when any fixes are made we can retest the fixes and follow the regression testing. Therefore, testing should occur in conjunction with each phase of the software development. 6. Will there be more defects in the design phase or in the coding phase? The design phase is more error prone than the execution phase. One of the most frequent defects which occur during design is that the product does not cover the complete requirements of the customer. Since the design phase drives the execution phase it is the most critical phase to test. The testing of the design phase can be done by reviews and inspections. On average, 60% of defects occur during design and 40% during the execution phase. 7. What are different types of verifications? Verification is static type of software testing. Code will not be executed. The product is evaluated by going through the code. Types of verification are: Walkthrough: Walkthroughs are informal, initiated by the author of the software product to colleagues for assistance in locating defects or suggestions for improvements. They are usually unplanned. Author explains the product; colleague comes out with observations and author notes down relevant points and takes corrective actions. Inspection: Inspection is a thorough word-by-word checking of a software product with the intention of locating defects, confirming traceability of relevant requirements etc. 8. Which test cases are written first: white box’s or black box’s? Normally black box test cases are written first and white box test cases later. In order to write black box test cases we need the requirement document and, design or project plan. All these documents are easily available at the start of the project. White box test cases cannot be started in the initial phase of the project because they need more architecture clarity which is not available at the start of the project. So normally white box test cases are written first. Black box test cases do not require system understanding but white box testing needs more structural understanding. And structural understanding is clearer in the later part of project, i.e. while designing and executing. For black box testing you need to only analyse from the functional perspective which is easily available from a simple requirement document. 9. What do entry and exit criteria mean in a project? Entry and exit criteria are a must for the success of any project. If you do not know where to start and where to finish then your goals are not clear. By defining exit and entry criteria you define your boundaries. For instance, you can define entry criteria that the customer should provide the requirement document or acceptance plan. If this entry criteria is not met then you will not start the project. On the other end, you can also define exit criteria for your project. For instance, one of the common exit criteria in projects is that the customer has successfully executed the acceptance test plan. 10. What is the difference between verification and validation? Verification is a review without actually executing the process while validation is checking the product by executing the source code. For instance, code review and syntax checking is verification while actually running the product and cross-checking the results is validation. 11. What is the difference between latent and masked defects? A latent defect is an existing defect that has not yet caused a failure because the corresponding sets of conditions are not yet met. A masked defect is an existing defect that hasn't yet caused a failure just because another defect has prevented that part of the code from being executed. 12. What's the difference between alpha and beta testing? Alpha testing is the acceptance testing done at the development site. Some organizations have a different visualization of alpha testing. They consider alpha testing as testing which is conducted on early, unstable versions of software. On the contrary beta testing is acceptance testing conducted at the customer end. In short, the difference between beta testing and alpha testing is the location where the tests are done. 13. What is coverage and what are the different types of coverage techniques? Coverage is a measurement used in software testing to describe the degree to which the source code is tested. There are three basic types of coverage techniques. • Statement coverage: This coverage ensures that each line of source code has been executed and tested. • Decision coverage: This coverage ensures that every decision (true/false) in the source code has been executed and tested. • Path coverage: In this coverage we ensure that every possible route through a given part of code is executed and tested. 14. Can you explain the concept of defect cascading? Defect cascading is a defect which is caused by another defect. One defect triggers the other defect. For instance, in the accounting application shown here there is a defect which leads to negative taxation. So the negative taxation defect affects the ledger which in turn affects four other modules.