Black Box Testing: An In-depth Tutorial with Examples and Techniques

In this tutorial, using my industrial experience in software testing, let's familiarize with the types and techniques of black box testing along with its process, advantages, disadvantages and some automation tools to test it other than manual testing.

We will also learn about the differences between white box testing and black box testing. 

List of “Black Box Test Techniques” Tutorials:

Tutorial #1: What is Black Box Testing
Tutorial #2: What is White Box Testing
Tutorial #3: Functional Testing Simplified
Tutorial #4: What is Use Case Testing
Tutorial #5: Orthogonal Array Testing Technique

Techniques
Tutorial #6: Boundary Value Analysis and Equivalence Partitioning
Tutorial #7: Decision Table Testing
Tutorial #8: State Transition Testing
Tutorial #9Error Guessing
Tutorial #10: Graph-Based Testing Methods

Almost all of us perform black box testing every day! 

Whether we have learned or not, we all have and performed black box testing many times in our day to day life!!

Black box testing

From the name itself you can probably understand that it implicates interacting with the system, that you are testing as a mystery box. It means that you are not knowledgeable enough about the internal working of the system but you know how it should behave.

If we take an Example to test our car or bike, we always drive it to make sure that it doesn’t behave in an unusual way. See? We already have done black box testing.

What is Black Box Testing?

Black box testing, which is also known as behavioral, opaque-box, closed-box, specification-based or eye-to-eye testing, is a Software Testing method that analyses the functionality of a software/application without knowing much about the internal structure/design of the item that is being tested and compares the input value with the output value.

The main focus in black box testing is on the functionality of the system as a whole. The term ‘behavioral testing' is also used for black box testing. Behavioral test design is slightly different from the black-box test design because the use of internal knowledge isn't strictly forbidden, but it's still discouraged.

Each testing method has its own advantages and disadvantages. There are some bugs that cannot be found using the only black box or only white box technique. Majority of the applications are tested by black box method. We need to cover the majority of test cases so that most of the bugs will get discovered by a black-box method.

This testing occurs throughout the software development and Testing life cycle i.e in Unit, Integration, System, Acceptance, and regression testing stages.

This can be both functional or non-functional.

Black box testing

Types of Black Box Testing

Practically, there are several types of black box testing that are possible but if we consider the major variant of it then below mentioned are the two fundamental ones.

#1) Functional Testing

This 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 that 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 several non-functional aspects as well 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

Black box testing tools are mainly record and playback tools. These tools are used for regression testing to check whether new build has created any bug in previous working application functionality.

These record and playback tools record test cases in the form of some scripts like TSL, VB script, Javascript, Perl, etc.

Here is One Recommended BBT Tool:

#1) Ranorex Studio

ranorex-studio

Ranorex Studio supports black box testing for desktop, web, and mobile applications.  Record user interactions, add validations, specify conditions for execution, and use data from an Excel file or SQL database, all without coding.

Selenium WebDriver is built-in for easy cross-browser testing. Ranorex Studio integrates with your CI/CD/DevOps tools including Jira, Bugzilla, Jenkins, Bamboo, and many more. 

=> Click here to start your 30-day free Ranorex Studio trial


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 us understand each technique in detail.

#1) Equivalence Partitioning:

This technique is also known as Equivalence Class Partitioning (ECP). In this technique, input values to the system or application are divided into different classes or groups based on its similarity in the outcome.

Hence, instead of using each and every input value we can now use any one value from the group/class to test the outcome. In this way, we can maintain the test coverage while we can reduce a lot of rework and most importantly the time spent.

For Example:

Equivalence Partitioning

As present in the above image, an “AGE” text field accepts only the numbers from 18 to 60. There will be three set of classes or groups.

Two invalid classes will be:

a) Less than or equal to 17.

b) Greater than or equal to 61.

One valid class will be anything between 18 to 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 anyone value from each set of the class is sufficient to test the above scenario.

=> Recommended Read – What is Equivalence Partitioning?

#2) Boundary Value Analysis:

From the name itself, we can understand 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 means the values near the limit where the behavior of the system changes. In boundary value analysis both the valid inputs and invalid inputs are being tested to verify the issues.

For Example:

Boundary Value Analysis

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 that, 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 interest rate for the Male senior citizen as 10% and for rest of the people 9%.

Decision Table

In this example condition, C1 has two values as true and false, condition C2 also has two values as true and false. The number of total possible combinations would then be four. This way we can derive test cases using a decision table.

#4) State Transition Testing:

State Transition Testing is a technique that is used to test the different states of the system under test. The state of the system changes depending upon the conditions or events. The events trigger states which become scenarios and a tester needs to test them.

A systematic state transition diagram gives a clear view of the state changes but it is effective for simpler applications. More complex projects may lead to more complex transition diagrams thus making it less effective.

For Example:

State Transition Testing

#5) Error Guessing:

This is a classic example of experience based testing.

In this technique, the tester can use his/her experience about the application behavior and functionalities to guess the error-prone areas. Many defects can be found using error guessing where most of the developers usually make mistakes.

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 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:

Different independent versions of the same software are used to compare to each other for testing in this method.

How to 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. A proper 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.
  • The 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 it is recurring or not.

Advantages and Disadvantages

Advantages:

  • The tester need not have a technical background. It is important to test by being in the user's shoes and think from the user’s point of view.
  • Testing can be started once the development of the project/application is done. Both the testers and developers work independently without interfering in each other’s space.
  • It is more effective for large and complex applications.
  • Defects and inconsistencies can be identified at the early stage of testing.

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 are possibilities of testing less and skipping all possible inputs and their output testing.
  • A Complete Test Coverage is not possible for large and complex projects.

Difference between White Box Testing and Black Box Testing

Given below are few differences between the both:

Black Box TestingWhite Box Testing
It is a testing method without having knowledge about the actual code or internal structure of the applicationIt 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 testIt concentrates on the actual code – program and its syntax's
Black box testing requires Requirement specification to testWhite Box testing requires Design documents with data flow diagrams, flowcharts etc.
Black box testing is done by the testersWhite box testing is done by Developers or testers with programming knowledge.

Conclusion

These are some of the basic points regarding Black box testing and the overview of its techniques and methods.

As it is not possible to test everything with human involvement with 100 percent accuracy, if the above-mentioned techniques and methods are used effectively it will definitely improve the quality of the system.

To conclude, this is a very helpful method to verify the functionality of the system and identify most of the defects.

Hope you would have gained an in-depth knowledge of Black Box Testing technique.

Recommended Reading

152 thoughts on “Black Box Testing: An In-depth Tutorial with Examples and Techniques”

  1. Thanks Namita
    Actually you could have observed that most of the testers in India are Black box testers. There is need to give more emphasis on this topic. So I will keep writing some more topics on Black box testing and practical methods.

  2. Really ! You have very good skill of representing this !
    I want to read more and more about testing through this blog….

    Thanks

  3. can we test the application without having any system this question was asked in interview.And also how to generate the reports.pls suggests me

    regards
    raj

  4. White box testing is based on knowledge of the internal logic of an application’s code. Also known as Glass box Testing. Internal software and code working should be known for this type of testing. Tests are based on coverage of code statements, branches, paths, conditions.

  5. Hi Vijay

    Recently I came across the foll. terms:

    Grey Box testing
    Red Box testing
    Yellow Box testing &
    Green Box testing

    Could u pls explain the above types of testing in detail. Thanks.

  6. 1.What is the Difference Between Test Cases and Test Scenarios????????

    2. Canu plz tell me the exacr definition of Test Scenario??

  7. hi sivaguru,

    test Scenario specifies required test conditions to apply on a build.
    where as test case specifies detailed procedure to apply the test conditions on a build.

    This is the best answer that i can give…….

  8. hello to everyone, i want to know the basic concepts of testing tools in brief individually, can u people let me know from where can i get this information

    thank u

  9. @ varsha, bala
    “”Red Box testing
    Yellow Box testing &
    Green Box testing””,
    there is no terminology like this in testing industry, some can say it is protocol testing-redbox, or error message testing-red box, warning message testing-yellow box and green box- environmental testing, of cource white, black, grey box testing is there. Or else why it is called by red, green, yellow box testing, anyway it is not due to the icon\symbol present in the warning or error messages.

    Vijay

  10. hey guys, trull i learn a lot from u. …thanks

    Can anyone explain to be more in details. wat is error guessing?

    thankx

  11. Hi,
    I want to know what exactly do the term exhaustive testing ? IS it possible to carry it out ?

    Thanks,
    Rashmi

  12. hey guys, trully i learnt a lot from u. …thanks

    Can anyone explain more in details. ….. Tools in Black Box Testing

  13. Hi Vijay,

    Currently, I’m working on a functional test cases document. But I’m having difficulty in determine which of my user requirement is consider to be a functional requirement and which are non-functional. For example, one of the requirements said that the system should be able to send the request to dedicated travel agent and the other requirements said that the system should be able to convert monthly report into a .csv format. Do you think those 2 requirements consider as functional requirement? Anyone can help?.

  14. Hi Nodeen,

    It seems we have similar projects at hand and I am wondering if you would be happy to share your experience on the forum. My task is to review lines of code for inherent vulnerabilities using black-box testing. kindly holler asap

  15. @Abhirup
    Manual Testing is as good as any other testing skills. Its just the level of specilization that matters. I’ve seen many manual functional testers went on to become Business Analysts and further more. So if you are interested in testing (be it manual), just put great efforts and you will achive great results.

  16. Hi,

    Really nice to read the article.

    Generally we develop the Test Plan in a xl sheet with diff. info. in different Tabs.

    Can u provide me a Standard Test Plan including all diff. types of info. !! It will be vey helpful for me….

    Thanks

    A. Adhikary

  17. hello
    I m doing thesis on black box testing.what r problems occured in black box testing. plz send me some important links that can help me in my thesis

  18. Hi,
    What a comprehensive article on Black Box Testing! It was thoroughly enlightening too! Fantastic work, sir!

    I have known only Indusa Infotech to be doing these services in Ahmedabad. Can you name some more companies in Ahmedabad which offer black box testing services..

    Thanks again for the insight

  19. i am testing java application by using jmeter testing tool.
    i had prepared functional test test case summary report.now i want to prepare load test report. please any one give some idea how to prepare load test report.
    mail: sunaruna84@gmail.com
    with regards
    sundar

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