Overview of Test Design Techniques in Software Development

What are test design techniques?

Test design is a significant step in the Software Development Life Cycle (SDLC), also known as creating test suites or testing a program. In other words, its primary purpose is to create a set of inputs that can provide a set of expected outputs, to address these concerns:

  • What to test and what not to test
  • How to stimulate the system and with what data values
  • How the system should react and respond to the stimuli

test design techniques

Therefore, various techniques exist for test design and execution. It is understandably crucial to utilize some effective test design techniques since software development is getting more complicated. Generally, software testing design techniques help you write better test cases and optimize testing processes. It also helps reduce the time of executing test cases while escalating test coverage. In this post, I will discuss the overview of software testing design techniques.

The importance of test design techniques

Test design techniques are applied to satisfy the goals of every individual in software development projects, including testers. Although the main purpose is to ensure that the products meet the expectations of clients and their businesses, these techniques allow testers to execute the test effortlessly based on various risk factors. Here is a checklist of standards that a smooth testing process meets:

  • Gather information to understand users’ requirements
  • Derive all important business scenarios
  • Design test scenarios for every derived critical business scenarios
  • Assign all planned test scenarios to different test cases

Then, you will have to choose a test design technique for each requirement. At this point, if things are correctly implemented, you can make significant changes that affect your ROI extraordinarily.

Two of main advantages of techniques lie on their consistency and repeatability:

  • Possibility to reproduce a test:
    At several testing phases, testing techniques are considered as a set of rules help ensure a minimum level of consistency. Testers, indeed, would work much more efficiently with a base, thereby reducing a significant amount of effort in later fixing.
  • Increasing of the found bugs:
    Test design techniques can also be used as analytical tools. When applying techniques to elements, we often see problems in the definition of those elements

Types of test design techniques

Each of these test design techniques is suitable for identifying a certain type of error. The new standard ISO 29119 Software Testing includes the following techniques:

type of test design technique

1. Specification-based or Black-box techniques

  • Equivalence Partitioning:
    The idea of this approach is grouping the inputs with the same attributes to partitions. Code is not visible to testers. Your task is to pick one condition out of each partition, which covers all possible scenarios, to execute test cases. If a condition of a partition is valid, other conditions are valid too. Likewise, if a condition in a partition is invalid, other conditions are also invalid. This helps reduce the number of test cases.
  • Boundary Value Analysis:
    This is one of the software testing techniques in which test cases are designed to include values at the boundaries. If the input is within the boundary value, it is considered ‘Positive testing.’ If the input is outside of the boundary value, it is considered ‘Negative testing.’ The goal is to select test cases to execute boundary values. In other words, the behavior of Negative testing is more likely to be incorrect than the behavior of Positive testing; and boundaries are an area in which testing is more likely to yield defects.
  • Decision Table Testing:
    This technique can be used in test design because it helps testers explore the effects of combining different input values when adhering business rules. A Decision Table is a tabular representation of conditions versus test actions. Conditions are considered as inputs, while actions are considered as outputs.
  • State Transition Diagrams:
    Using this approach, the tester analyzes the behavior of an application under test (AUT) for different input conditions in a sequence. You can provide both positive and negative input test values and record the system behavior. Any system in which you get a different output for the same input is a finite state system.
  • Use Case Testing:
    Use case testing is a functional testing technique, meaning programming skill is not required. It helps the tester determine which test scripts are executed on the entire system from the beginning to the end of each transaction.

2. Structure-based or White-Box techniques

  • Statement Coverage or Line Coverage:
    In this technique, every statement in the source code is executed at least once. Thereby, we can check what the source code is and is not expected to do. However, we cannot test the false condition in the source code.
    Statement coverage = (No. of statements Executed/Total no. of statements in the source code)*100
  • Condition Coverage or Predicate Coverage:
    Condition coverage is seen for Boolean expression. Condition coverage ensures whether all the Boolean expressions have been covered and evaluated to both TRUE and FALSE.
  • Decision Coverage or Branch Coverage:
    Test coverage criteria require enough test cases so that each condition in a decision takes on all possible outcomes at least once, and each point of entry to a program or subroutine is invoked at least once. That is, every branch (decision) is either true and false. It is helpful to invalidate all branches in the code to make sure that no branch leads to any abnormal behavior.
  • Multiple Condition Coverage:
    Every combination of ‘true’ or ‘false’ for the conditions related to a decision has to be tested in this technique.

3. Experience-based technique

  • Exploratory Testing:
    Usually, this process is carried out by domain experts. They perform testing just by exploring the functionalities of the application without having the knowledge of the requirements. Testers can explore and learn the system while using these techniques. High severity bugs are found very quickly in this type of testing.
  • Error Guessing:
    Error guessing is one of the testing techniques used to find bugs in a software application based on the tester’s prior experience. In Error guessing, no specific rules are applied.

Learn more details about these techniques at Different Types of Test Design Techniques You Must Know

Choosing the right technique

choose the right technique

As mentioned, choosing the technique is the most decisive step. This step is dependent on these factors:

  • Type of system or software application:
    Testing techniques are mainly determined based on requirements for the domain of the application. Moreover, these techniques are applied differently between mobile and web applications. 
  • Regulatory standards:
    It is evident that your selection of techniques must follow conventional rules of, and approved by the IT industry.
  • Customer’s requirements:
    Selection of techniques varies and is based on the customer requirements. If your customer does not provide any provision, you have to choose the experience-based approaches. 
  • Level and type of risk:
    Risks may include lack of requirement, equipment or anything related to quality assurance. Both high-level and low-level design techniques can be applied. 
  • Test objectives:
    Test objectives are important because it narrows down the scope of testing activities. Based on that, you can select the most suitable techniques for your project.
  • Tester’s skill and knowledge: 
    This plays a very crucial role in the selection of techniques since it depends on the availability of test documents like requirement document, analysis report, design document etc. The perception of testers about the application and experience on test execution help to figure out defects quickly, and make the product a quality one. 
  • Time and budget:
    Some projects are short-term, and some are long-term. Based on the project you need to choose techniques. You need to cleverly calculate the budget for each project. For small budgets, cost-effective approaches should be taken.
  • Application development life cycle:
    The application development life cycle has different stages, parallel to testing stages. Different stages of development and testing require different techniques.
  • Previous experience in types of defects tracked:
    This is a type of experience-based techniques on defects that you may encounter in the testing life cycle. What’s more, you can replicate the same situation and catch the errors that met previously.

Conclusion

While I have discussed aspects of test design techniques, I want to emphasize that a poorly designed test would lead to undesirable results or worse, fail to identify defects. Besides, I will discuss the types of designing techniques, their benefits, when to use, and the challenges that lie in each in the next article. Hope this helps!

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