Behavioral, opaque-box, closed-box, specification-based, and eye-to-eye testing are other names for black box testing.
This software testing technique compares the input value with the output value while analyzing the functioning of a program or application without having a thorough understanding of the underlying organization or design of the object under test.
Black box testing is primarily concerned with the overall functionality of the system.Black Box Testing is often referred to as “Behavioral Testing.”
The use of internal knowledge is not legally prohibited, but it is nevertheless discouraged, which makes behavioral test design slightly different from black-box test design. Every testing technique has pros and cons of its own. Some bugs are impossible to find with just the black box or white box techniques.
The Black Box approach is used to test most of the apps. In order for the Black-Box approach to find the majority of the defects, we must cover the majority of test cases.
This testing takes place in the Unit, Integration, System, Acceptance, and Regression Testing phases of the Software Development and Testing Life Cycle.
This can be either Functional or Non-Functional.
Types of Black Box Testing
Although there are many different kinds of Black Box Testing in practice, if we look at a significant variation, the two basic ones are as follows.
#1) Functional Testing
This testing type deals with the functional requirements or specifications of an application. Here, different actions or functions of the system are being tested by providing the input and comparing the actual output with the expected output.
For example, when we test a Dropdown list, we click on it and verify if it expands and all the expected values are showing in the list.
Few major types of Functional Testing are:
- Smoke Testing
- Sanity Testing
- Integration Testing
- System Testing
- Regression Testing
- User Acceptance Testing
=> Read More on Functional Testing
#2) Non-Functional Testing
Apart from the functionalities of the requirements, there are even several non-functional aspects that are required to be tested to improve the quality and performance of the application.
Few major types of Non-Functional Testing include:
- Usability Testing
- Load Testing
- Performance Testing
- Compatibility Testing
- Stress Testing
- Scalability Testing
=> Read More on Non-Functional Testing
Black Box Testing Tools
The primary purpose of black box testing equipment is to record and replay data. Regression testing uses these technologies to see if a fresh build has introduced any issues in the functionality of an application that was previously functional.
Test cases are recorded using scripts such as TSL, VB, Javascript, Perl, and others via these recording and replaying tools.
Black Box Testing Techniques
In order to systematically test a set of functions, it is necessary to design test cases. Testers can create test cases from the requirement specification document using the following Black Box Testing techniques:
- Equivalence Partitioning
- Boundary Value Analysis
- Decision Table Testing
- State Transition Testing
- Error Guessing
- Graph-Based Testing Methods
- Comparison Testing
Let’s understand each technique in detail.
#1) Equivalence Partitioning
Another name for this method is Equivalence Class Partitioning (ECP). This method divides the system’s or application’s input values into various classes or groups according to how similar the results are.
As a result, we can now verify the result using any single value from the group or class rather than needing every single input value. In this manner, we may minimize the amount of rework and, most importantly, the time spent, while maintaining test coverage.
For Example:
As present in the above image, the “AGE” text field accepts only numbers from 18 to 60. There will be three sets of classes or groups.
Two invalid classes will be:
a) Less than or equal to 17.
b) Greater than or equal to 61.
A valid class will be anything between 18 and 60.
We have thus reduced the test cases to only 3 test cases based on the formed classes thereby covering all the possibilities. So, testing with any one value from each set of the class is sufficient to test the above scenario.
Recommended Read => What is Equivalence Partitioning?
#2) Boundary Value Analysis
The name itself defines that in this technique, we focus on the values at boundaries as it is found that many applications have a high amount of issues on the boundaries.
Boundary refers to values near the limit where the behavior of the system changes. In boundary value analysis, both valid and invalid inputs are being tested to verify the issues.
For Example:
If we want to test a field where values from 1 to 100 should be accepted, then we choose the boundary values: 1-1, 1, 1+1, 100-1, 100, and 100+1. Instead of using all the values from 1 to 100, we just use 0, 1, 2, 99, 100, and 101.
#3) Decision Table Testing
As the name itself suggests, wherever there are logical relationships like:
If
{
(Condition = True)
then action1 ;
}
else action2; /*(condition = False)*/
Then a tester will identify two outputs (action1 and action2) for two conditions (True and False). So based on the probable scenarios a Decision table is carved to prepare a set of test cases.
For Example:
Take an example of XYZ bank that provides an interest rate for the Male senior citizen as 10% and 9% for the rest of the people.
In this example condition, C1 has two values as true and false, C2 also has two values as true and false. The total number of possible combinations would then be four. This way we can derive test cases using a decision table.
#4) State Transition Testing
One method for testing the various states of the system being tested is state transition testing. Depending on the circumstances or occurrences, the system’s status varies. A tester must test the states that are triggered by the events, which turn into scenarios.
Although it works well for basic applications, a systematic state transition diagram provides a clear perspective of the state transitions. Complex projects might result in more intricate transition diagrams, which would reduce their effectiveness.
For Example:
#5) Error Guessing
An iconic illustration of experience-based testing is this.
With this method, the tester can guess the regions that are prone to errors by using his or her knowledge of the functionality and behavior of the program. Error guessing, where the majority of developers typically make blunders, can reveal a lot of problems.
Few common mistakes that developers usually forget to handle:
- Divide by zero.
- Handling null values in text fields.
- Accepting the Submit button without any value.
- File upload without attachment.
- File upload with less than or more than the limit size.
#6) Graph-Based Testing Methods
Each and every application is a build-up of some objects. All such objects are identified and the graph is prepared. From this object graph, each object relationship is identified and test cases are written accordingly to discover the errors.
#7) Comparison Testing
In this method, different independent versions of the same software are used to compare to each other for testing.
How do I do Step-wise?
In general, when a systematic process is followed to test a project/application then quality is maintained and is useful in the long run for further rounds of testing.
- The foremost step is to understand the requirement specification of an application. Properly documented SRS (Software Requirement Specification) should be in place.
- Using the above mentioned Black Box Testing techniques such as Boundary Value Analysis, Equivalence partitioning etc, sets of valid and invalid inputs are identified with their desired outputs and test cases are designed based on that.
- The designed test cases are executed to check if they Pass or Fail by verifying the actual results with the expected results.
- Failed test cases are raised as Defects/Bugs and addressed to the development team to get it Fixed.
- Further, based on the defects being fixed, the tester retests the defects to verify if they are recurring or not.
Advantages and Disadvantages
Advantages
- Technical expertise is not required of the tester. It is crucial to test by putting oneself in the user’s position and considering things from their perspective.
- After the project or application is developed, testing can begin. The developers and testers operate separately, respecting each other’s personal space.
- For complicated and large-scale applications, it works better.
- Early on in the testing process, flaws and irregularities might be found.
Disadvantages
- Without any technical or programming knowledge, there are chances of ignoring possible conditions of the scenario to be tested.
- In a stipulated time there is a possibility of testing less and skipping all possible inputs and their output testing.
- Complete Test Coverage is not possible for large and complex projects.
Difference Between White Box Testing and Black Box Testing
Given below are some of the differences between the two:
| Black Box Testing | White Box Testing |
|---|---|
| It is a testing method without having knowledge about the actual code or internal structure of the application. | It is a testing method having knowledge about the actual code and internal structure of the application. |
| This is a higher level testing such as functional testing. | This type of testing is performed at a lower level of testing such as Unit Testing, Integration Testing. |
| It concentrates on the functionality of the system under test. | It concentrates on the actual code – program and its syntax’s. |
| Black box testing requires Requirement specification to test. | White Box testing requires Design documents with data flow diagrams, flowcharts etc. |
| Black box testing is done by the testers. | White box testing is done by Developers or testers with programming knowledge. |
Conclusion
These are some fundamental ideas about Black Box testing, along with a summary of its approaches.
Since it is impossible to verify everything with human involvement with 100% accuracy, the system’s quality will undoubtedly be improved if the aforementioned strategies and methodologies are applied successfully.
In summary, this is an extremely useful technique for confirming the system’s operation and detecting the majority of its flaws.
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What are the Levels of Testing in Software Engineering
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