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Test Case Design Techniques


Software Development Life Cycle (SDLC) is a amalgamation of various components, which are combined together to form an impeccable software system or application, with outstanding features and qualities. However, the success of any project is highly dependent on the testing done on it, whose success is further dependent on how the test cases are designed and written. Therefore, to ensure optimum software development it is necessary to design test cases properly, using best design techniques. Hence, to help you with the process, following is a detailed discussion on test case design techniques.

Importance of Test Cases:

Test case is one of the significant components of the testing phase. These are the predefined conditions & variables, which are used to validate that the software & application along with its features, are working properly and are in compliance with the stated requirements and standards. These are extremely vital for the success of the testing process as well as the whole project. Hence, test cases work as a tool or manual that clarify what needs to be done to test a system and increase the productivity of the testing process.

Test Case Development Process:

Test case designing is a very important and time consuming tasks that requires ample care and attention. These are the guiding steps for testers and help them understand & execute the testing process. A well written test case makes the process of testing hassle free and smooth, and saves time and efforts of the testers. Therefore, it is vital for the test case developers to make sure that the test cases are written appropriately and have all the required details about the software under test (SUT). Moreover, during the test case development process it is necessary for the developers to consider the following documents to ensure effective test case development. These documents are:

  1. Test Case Specification: Developed during the test development phase, this document includes the a detailed summary of the scenarios that require testing, along with the information about how often they will be tested and its testing process. This document is developed by the organization responsible for the formal testing of the software system or application, as they simplify the process of testing. Other details included in test case specification documents are:
    • Specifies the purpose of the specific test.
    • Identifies the required inputs and expected outputs.
    • Provides a step-by-step procedures for executing the test.
    • Outlines the pass and fail criteria for determining acceptance.
    • Defines exact set-up & inputs for one test case.
  2. Test procedure Specification: Another important document that needs to be considered during the test case development process is test procedure specification. This document consists the details of how the team of testers physically or manually run test. Moreover, it offers an insight into the required physical set-up as well as the steps and procedure that needs to be followed. According to IEEE 829, this document can be developed by from both test case specification and Test Design and is mainly used by Quality Assurance group.

Test Case Design Techniques:

Divided mainly into three major categories, test case design techniques are crucial verifications steps that are created to design a software or application that is free from various kinds of defects and issues. The purpose of these techniques is to test the functionalities and features of the software with the assistance of some effective test cases. Test case design techniques ensure that the products meet the expectations of client’s and their business, by enabling the testing team to work in a systematic manner. In short, these techniques allow software developers to execute the test effortlessly, based on the various risk factors.

The 3 categories of test case design techniques are:

  1. Specification Based or Black-Box Techniques.
  2. Structure Based or White-Box Techniques.
  3. Experience Based Techniques.

Specification Based Test Case Design Techniques:

Specification based or Black Box test case design techniques are used to design test cases in a systematic manner. These use external description of the software such as technical specifications, design, client’s requirements, and more, to derive test cases. With the assistance of these test case design techniques, testers are able to develop test cases that save testing time and allow full test coverage.

Specification based or black box test case design techniques are further divided into five categories, which are mentioned below:

  1. Equivalence Partitioning: It's a method of dividing or partitioning the test input data into number of classes having equivalent number of data, which is then used to derive and design test cases for each class or partition, at least once time. This helps in reducing the number of test cases, significantly.
  2. Boundary Value Analysis: This is the most advantageous and important specification based testing technique, which is used to explore errors in the software product at the extreme ends of the input domain, i.e. at boundaries, and is used accordingly to derive and design test cases.
  3. Decision Tables: A technique of designing test cases, decision tables uses different combinations of inputs and their corresponding output based on the variant types of conditions, scenarios, adhering to different business rules.
  4. State Transition Diagrams/Tables: It's an approach of perceiving a software product as a system having a finite number of states of different types, where transition from one state to another is guided by some certain rules to response or behave differently for different input. This type of specification based technique is appropriate for systems that have implemented workflow within them.
  5. Use Case Testing: This method of test case testing derives test conditions from the test the use case. Here, the test cases are designed to execute business scenarios and user end functionalities. With the assistance of use case testing, one can easily identify test cases that cover the entire system, on a transaction by transaction basis from the start of the testing to its end. This technique, therefore, is used to derive test cases covering end-to-end software product evaluation.

Structure Based or White Box Technique:

The structure based or white box techniques designs test cases based on the internal structure of the software program and code. These techniques go into minute details of the developed code and tests them one by one. Performed mainly by the developers, structure based techniques require proper knowledge of software code, its internal structure, and design and help developers in verifying the various components of the system. Here, different test cases are derived to exercise the loop once or multiple times, regardless of software system’s functionality. Structure based or white box test case design technique is further divided into five categories, which are:

  1. Statement Testing & Coverage: This is the weakest criteria and least preferred metric for checking test coverage. Here, test scripts are designed to execute code statements. The main purpose of this technique to calculate the percentage of executable statements that are exercised by test suit.
  2. Decision Testing Coverage: Also known as branch testing, decision testing coverage is where the test design techniques exercise the percentage of the outcome of the decisions. Here, the test coverage is measured by the percentage of decision points, which are executed out of the total decision points in the application. This technique is stronger than statement testing and coverage.
  3. Condition Testing: This type of structure based techniques involves 100% coverage of the code. Here, each condition of the code coverage is executed at least once. In coverage testing, test cases are designed in such a way that the condition outcomes are easily executed.
  4. Multiple Condition Testing: Here, the main focus is on testing different combinations of condition outcomes to get 100% coverage. To ensure this, two or more test scripts are required, which becomes a bit exhaustive and difficult to manage.
  5. All Path Testing: All path testing is the strongest structure based test case design technique, which involves using the source code of a program to find every executable path. This technique of test case designing helps determine all the faults within a particular code.

Experience Based Techniques:

Though test cases are mainly designed systematically on the basis of various requirements and specification, it is quite important to use experience based techniques also. These are non-systematic testing techniques that are highly dependent on people’s skills, knowledge, and expertise. With the assistance of these techniques, software engineers are capable of finding technical as well as non-technical issues and defects in the test cases. Hence, types of experience based techniques are:

  1. Exploratory Testing: Usually conducted by business analysts and other business experts, exploratory testing is used to test application without any formal documentation of test cases, test conditions, & test scripts. This is hands-on testing approach, wherein testers are involved in minimum planning and maximum test execution. In exploratory testing, test design & test execution are performed simultaneously.
  2. Error Guessing: A widely used technique, error guessing is highly dependent on the skills, intuition, and experience of the testers. Here, testers have the freedom to anticipate the errors based on their experience, availability of defect data, and their knowledge of product failure.

Things to Consider while Choosing Test Design Techniques:

While deciding the type of test design techniques, there can be several factors that can affect the choice of testers and developers. From technical attributes, client’s requirements, and project specifications to other necessary factors like time and budget, the reasons for choosing one test case design technique over other can be numerous. Therefore, here is a list of some crucial factors are considered while choosing test design techniques.

  • Risks & Objectives: The objective and purpose of each software testing process differs from another, hence their requirements for test design technique also differs from each other. Moreover, the risks of testing also vary from one another and are therefore taken into considerations while choosing design techniques.
  • Type of System & Dev Cycle: Another factor that affects the choice of design techniques is the type of system (embedded, financial, graphical, etc.) and development cycle used by the program.
  • Regulatory Standards: Considering regulatory standards is an important factor. These are the common regulatory standards that are recognized internationally and followed by software testers everywhere.
  • Time & Budget: Time and budget play an extremely important role in choosing designing techniques. Without time & budget constraints, testers can easily experiment with multiple techniques. However, these constraints force them to choose a technique that enables them to get accurate outputs within a limited period of time.
  • Knowledge & Experience: Tester’s knowledge of the techniques and the project, along with their experience has a great impact on their choice. Their experience of test execution, defect detection, and delivering a quality product enables them to choose the appropriate designing technique.

Conclusion:

Test case design techniques are a significant part of software testing as they are directly responsible for success of software testing. With the assistance of these techniques, one can effortlessly test various components of the software, such as its internal structure, codes, design, test cases, and more. Moreover, they enable software developers and testers to create and design test cases that simplify the process of testing and help them execute test cases effortlessly. Therefore, if you want to ensure the quality, effectiveness, reliability and consistency of your software product, it is vital for you to choose the right test case design technique.