4 Black-Box Testing Techniques

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A working principle of black-box testing is similar to its name. Testers are interested in data input and output, excluding internal program structure.

For engineers, a program code, design, internal structures are a black box in which testing is not conducted.

The main goal of black-box testing is checking the whole system in the presence of external factors that lead to failures. Also, black-box testing covers performance and usability issues, functionality from the user’s perspective, the system’s interaction with the inputs, etc.

There is no need to know any programming language to conduct this test, so it is a huge benefit for beginners. Among other advantages are independence between developers and testers, test cases can be designed as soon as software functional specifications are complete, acceptance for a large system.

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On the other hand, beginner’s lack of technical knowledge can lead to an omission of possible test cases to be tested. Test cases writing may be a long and problematic process due to complications identifying inputting data caused by limited testing time.

Let’s consider the best black-boxing testing techniques which are perfect for professional testers and your QA company.

Equivalent Class Partitioning

The benefit of this technique is reducing the testing time as a consequence of split off test cases on groups and modules. In this technique, input values are separated into classes and groups according to their similarity. So instead of inputting every particular value, we can use any value of the group to test to get results.

For example, you’re testing a site and want that only people elder 18 have access to it. You’re separating values on two groups: 1) under 18; 2) higher or equal 18.

All integers under 18 are invalid, and all integers higher 18 are valid. Thus, you have only two test cases based on similar values.

Boundary Value Analysis

This technique is often used with Equivalent Class Partitioning. As we know, the ECP technique divides input data into groups with valid and invalid values. This approach may cause many failures due to boundary values. Boundary values are minimum or maximum value in the range.

As an example, consider a program that accepts donated from $5 to $15 only. 5, in this case, is a minimum value and 15 is a maximum one. So, 5 and 15 are boundary values of the program. Everything below 5 and above 15 is invalid values. An error can happen if a tester doesn’t set the equal value of inputs, and the program won’t accept $5 donat but starting at $6. To prevent failures like these testers, use Boundary Value Analysis.

Boundary Value Analysis, also known as “Range Checking”, is a technique that identifies errors in input and output boundary values. This technique can be used at all test levels.

State Transition Testing

This technique tracks the state and behavior of the system under changing input values. Each system has its number of finite states to which can lead various conditions. At different input values, as valid and invalid, can bring out different system transitions in a system. For example, you enter your name in a login field, and if the name is correct, you’ll get access to your account. And if the name isn’t valid, the system will error. In case if you changed your name and would try to input the old name system would error again due to system state has changed. So, the same input can lead to a different output.

This technique is mostly used when a system has a sequence of actions and associated various condition which can impact on final results of these actions. State Transition Testing can be highly detailed in important parts of the program and abstracted in less important.

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Decision Table Testing

This technique, also known as the cause-effect table, is applied in complicated and intricate scenarios with various input combinations to identify scenarios for business logic.

Two previous methods State Transition Testing and Boundary Value Analysis are appropriate for particular inputs and values.

But sometimes testers have a deal with different combinations of inputs which can lead to different results and with systems that work with particular business rules. In this case, we use Decision Table Testing to address the issue.

With this approach, various input combinations and associated results and system behavior are fixed in tables. It helps testers to identify better combinations according to business rules. With this approach, complicated business scenarios can be divided into test cases that simplify a test and development process.

However, this technique is very effective, but you can’t check all combinations due to high cost and high time-consuming. So, results depend on the chosen combination by testers.

Conclusion

So as you can see, black-box testing has many helpful techniques. Choosing the right one can help you rid off many problems associated with the testing process. You can merge and combine methods, experiment, or implement all techniques in your testing, but always remember about your client’s business goals.

See more software testing resources on EuroSTAR Huddle.

About the Author

Anastasia

Anastasia is a writer and part of a marketing team at testing software company Utor.
Find out more about @anastasia

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