Test design techniques help every software development project improve its overall quality and effectiveness. There’s a multitude of software testing techniques in the automation landscape. Each of them has its own strengths and weaknesses. This blog post will give an overview of some of the most popular techniques, divided into categories. But first and foremost, I suggest you learn the overview of Test Design Techniques in Software Development before seeing each technique in detail.
Specification-based or Black-box technique
Use these techniques to determine the external factors—such as technical specifications, design, and customer’s requirements, etc.—of a software program. Testers view the software as a black box with inputs and outputs. The purpose is to validate the quality and correctness without disrupting the internal details.
- 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.
Structure-based or White-Box techniques
This is a testing method in which the internal structure of applications is transparently seen and tested. The tester chooses inputs to exercise paths through the code and determines the appropriate outputs. Programming knowledge is required.
- 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.
These techniques are logically drawn from the experience in designing test cases and test conditions:
- 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.
These are only three test design techniques besides hundreds to choose from. Each one serves best for specific types of problems in software. If we use one more than the others, our test coverage will suffer. Remember to choose the most suitable technique for your projects, not the most popularly used one.
Most people want to make things perfect. Sometimes we evaluate the complexity of an upcoming goal or a problem. So, the fear to not complete it perfectly or "wrong" (Yeah, who are judges? 🤔) stops us even from trying.