When someone picks mistakes in our work, we take it as criticism, but some lucky people are paid to do this job. These people are known as Testers, and they test software applications. This may sound like an easy job, but testing is very tricky. 

For making the testing job more accessible, the Black-Box technique is divided into three parts: 

  • Black Box Testing- In Black Box Testing,the testing is done without the internal knowledge of the product.
  • White Box Testing- White box testing techniques analyze the internal structures, code structure, and software working rather than just the functionality.
  • Gray Box Testing- Gray Box testing combines black and white box testing. The testing is done with partial knowledge of the product’s internal structure.

Black box technique is used when software development functionality has to be tested without having internal coding. Acceptance tests are black box tests. It works on the software’s principles, specifications and requirements while prioritizing the input and output of the software.

Here is a detailed discussion to get a better insight into the Black Box testing technique.

What is Black Box Testing?

The Black Box Testing technique is a software testing process that includes a variety of designs and technologies that check software from outside without scanning the code.

Black Box testing acquires its name from the idea of the black box through which one can not decode the internal contents of the box and can only visualize and examine external structure.

Black Box Testing techniques refer to any software in which the functionalities of software applications are tested without knowing the internal code, design, structure, implementation details, and internal paths.

It mainly focuses on the input and output of software applications, totally based on software needs. It is also known as Specification-based testing or Behavioral Testing.

Difference Between a White Box Testing and Black Box Testing

  • In Black Box Testing, the internal structure is hidden; on the other hand, in white box testing, the internal structure of the codes is known to the testers.
  • The Black box testing is mainly done by testers, while developers do white box testing.
  • The Black box testing is applicable to the higher level of testing of software. In contrast, White box testing is applicable to the lower testing software.

How to do Black Box Testing?

The Black box testing technique involves testing external interfaces to ensure that the code meets the functional and non-functional requirements. Here are the various steps involved in Black Box Testing are:

  • Firstly, the requirements and specifications of the system are examined.
  • The tester chooses valid inputs (favorable test case scenario) to check whether SUT processes them correctly. Also, some invalid inputs (adverse test case scenario) are selected to verify that the SUT can detect them. Efficient and time-saving techniques are incorporated.
  • Tester governs expected results for all those inputs. 
  • Software tester established test cases with the selected inputs.
  • The software tester compares the actual outputs with the expected outcomes.
  • Defects, if any, are fixed.
  • Retest for confirmation.

Types of Black Box Testing

types of black box testing
types of black box testing

There are various types of Black Box testing in software engineering, but we consider only major types: functional, non-functional, and regression.

Functional Testing

The Black Box technique can test particular functions or features of the software. Functional testing checks User Interface, Database, API, and Security under test. For Example, if the right pin is entered, money can be transferred, and the transaction fails if the incorrect pin is entered.

Examples of Functional Testing are:

  • Unit Testing
  • Component Testing
  • System Testing
  • Smoke Testing
  • Sanity Testing
  • Integration Testing `
  • User Acceptance Testing

Non-functional Testing

Black box methodology can check additional aspects of the software other than features and functionality. A non-functional test revolves around “how” well the system performs its work.

This can check whether or not the software is:

  • Perform when the load is maximum.
  • Compatible to work with relevant devices or operating systems.
  • Easy to understand for its users.
  • Exposed to security threats.

Regression Testing

This type of Black Box Testing, regression testing is used to check if new software has any adverse effect on the existing ones. Regression testing is a process of selecting parts of test cases that have already been executed to ensure that the functionality has any irregularities.

In other words, it tests to make sure that the new codes do not have side effects on the existing codes. The regression testing tools are Quick Test Professional, Selenium, Rational Functional Tester. or QTP. 

Techniques of Black Box Testing

techniques of black box testing
  1. Equivalence Partitioning
  2. Boundary Value Testing
  3. Decision Table Testing
  4. State Transition Testing
  5. Error Guessing
  6. Comparison Testing

Let’s discuss these different black box testing techniques one by one in details

Equivalence Partitioning

This method is also known as Equivalence Class Partitioning (ECP). In this technique, input values are divided into groups according to the similarity in results. So instead of using every input, we can use one value from each group. This way, we can save time and reduce the amount of rework.

For Example, if the field receives an integer in the range 3 and 30, then:

Valid Equivalence Class Partition: 3 to 30 inclusive.

Invalid Equivalence Class Partition: Less than 3 or more than 30, decimal numbers or alphabets and other non-numeric characters.

Boundary Value Testing

As the name defines, we will focus only on the boundaries in this technique because many issues are found on the borders. The boundary is the value near the limit where the system’s behavior changes.

In this type of testing, both valid and invalid inputs are being tested to verify the issues.

For Example, an offer is only applicable for customers between 16 and 31. Therefore other values such as 16, 17, 31, or 32 can be tested to check whether the inputs are accepted.

Decision Table Testing

Decision Table testing is applicable for logical relationships. In this type of testing, outputs obtained depend on certain conditions. It is used where different test input conditions result in different outcomes. When a system has complex business rules, the decision table testing technique helps identify the correct test cases.

State Transition Testing

As the name shows, this testing is used to test the different states of the system under test. The situation of the system changes according to the conditions or events. This technique is helpful where you need to test different system transitions.

For Example, if the user wants to log in to any application but enters the password wrong, the account is locked after a particular number of attempts. Hence there is a transition from an available state to a locked account.

Error Guessing

This is Experience-based testing in which there is no specific method for identifying the error. This method depends upon the tester’s prior Experience and their foresight to guess where defects can occur in the future.

Common mistakes that developers usually forget are :

  • Handling null values in text fields.
  • File upload without attachment.
  • Divide by zero.
  • File upload is not within the fixed dimensions.

Comparison Testing

In this testing, different versions of the same software are compared for testing.

Advantages and Disadvantages of Black Box Testing

Further in this article, we will talk about some advantages and disadvantages of black-box testing techniques.

Advantages

Here are a few advantages of black-box testing techniques are:

  • It is not necessary to have a technical background, programming, or IT skills for black-box testing. It is important to think from the clients’ point of view. 
  • Black-Box Testing is suitable for complex applications.
  • Both software developer and tester can work independently without any interference.
  • Defects can be identified at early stages.
  • It is the best option for functional testing.
  • Test cases can be developed fast with the help of black box testings.
  • Helps in easy implementation of the application.
  • If there is any vagueness in the specification, it helps identify them.

Disadvantage

Along with advantages, Black box testing has a few disadvantages too. These are:

  • If the test inputs are more, it can be time-consuming and exhausting.
  • There is a high chance of repeating tests already performed by the programmer.
  • Without any technical knowledge, there are chances of ignoring possible conditions of the scenario to be tested.
  • Attaining no result at the end of a test is a significant probability.
  • The entire software is not tested as it can be time-consuming.
  • Entire testing is not possible for large and complex projects.

Related:- Unit Testing vs Functional Testing

FAQs Related to Black Box Testing

faqs related to black box testing

What is Black Box Testing?

The Black box testing technique is high-level testing whose main aim is to test functionalities from the behavioral point of view. The tester has no idea how the software was programmed.

Which errors are not identified by Black Box Testing?

Here are some errors that are not identified by black-box testing are:

  • Incorrect functions.
  • Improper flags that will be tested in a subsequent series of tests.
  • Wrong data placed in a global data area.
  • Typographical errors.
  • Data structure errors.

Does Functional Testing come under Black Box Testing?

Functional testing is a quality assurance(QA) procedure and a kind of black-box testing that mainly focuses on the application’s functions. It is performed by providing a specific input and checking if the output meets the software’s requirements and specifications.

Final words

To conclude, this is a beneficial method to verify the system’s functionality and identify most of the defects. The Black Box technique gives an overview of software performance and its output and reduces the chance of software failures at the user’s end. 

I hope you have gained an in-depth knowledge of the Black-Box Testing methodology from this article.