What is Black Box Testing

In the software testing domain, Black Box Testing is one of the easiest and most widely used methods to ensure software quality. It focuses on verifying the functionality of an application without looking into its internal code structure, making it ideal for testers who do not have programming knowledge.

In this article, you will learn more about Black Box Testing in detail.

Table of Contents:

• What is Black Box Testing?
• History and Evolution of Black Box Testing
• Types of Black Box Testing
• Ways of Black Box Testing Done
• What Does black Box Testing Focus On?
• Features of Black Box Testing
• Advantages of Black Box Testing
• Disadvantages of Black Box Testing
• Black Box vs White Box Testing vs Grey Box Testing
• Best Practices for Black Box Testing
• Tools and Frameworks Used for Black Box Testing
• Real-World Examples of Black Box Testing
• Conclusion

What is Black Box Testing?

Black Box Testing is a type of Software Testing method in which the tester does not know about the internal working of the software. In this method, the tester only tests what the software is doing, without knowing how it is doing it. It is done by the testers or sometimes end users, not by the developers.

For example, while using a calculator, you performed the addition of the two numbers, say 3 and 5. Now, do you check how the calculator is adding the numbers? No. You just check the answer that is 8.

In this testing, you only test the software based on the requirements.

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History and Evolution of Black Box Testing

Before discussing the details of the Black Box Testing in types. First, let us know about its origin and history. 

1. Early Days (1950s–1960s) – Birth of Software Testing

In the early 1950s, software development started growing with the early computers. Initially, the developers themselves tested their programs, and there was no formal testing method for the software. At this time, the testing was mainly manual and focused on checking the outputs as per the input, and this led to the idea of black box testing. 

2. Emergence of Black Box Testing (1970s)

When the software began to become more complicated, the need to separate the software from the testing started. In this era, the techniques of Functional testing were formally introduced.

3. Formalization and Techniques (1980s–1990s)

At this time, techniques like Equivalence Partitioning, Boundary Value Analysis, Decision Table Testing, and State Transition Testing came into the picture.

4. Automation and Tools (2000s)

When manual testing became a tough job for humans, there was a need for automation. Tools like Selenium, QTP (now UFT), TestComplete, etc., were introduced for black box testing. 

5. Agile and DevOps Era (2010s – Now)

Now, software is being built and released at a rapid pace. The teams now follow the Agile and DevOps methods to develop and test the software at the same time. Black box testing is used in every sprint or release. At present, tools like Selenium, Appium, and JMeter help do black box testing automatically. Testers now use black box tests to check how the app works on different devices, browsers, and networks.

6. Future Trends

The introduction of AI and Machine Learning is entering the picture in Black Box Testing. Self-healing test scripts, intelligent test case generation, and visual testing are evolving day by day. In the future, tests that fix themselves when the app changes are called self-healing tests.

Types of Black Box Testing

There are many types of black box testing, some of which are as follows:

1. Functional Testing

Functional testing mainly focuses on what the software does. It focuses on testing the features and behaviours of the application against the functional requirements or specifications. 

In this testing, the testers provide the inputs, observe the output, and also check if the output produced is the same as the expected output. It is performed mostly by the Software testers by using the test cases as per the requirements.

For example, testing a login page,

• After entering the correct username and password, you should be logged in.
• After entering an incorrect password, it should show an error.
• By clicking the Submit button, the form should save data.

2. Non-Functional Testing

Non-Functional Testing mainly focuses on how well the software works, rather than what it does. It focuses on the attributes like speed, performance, security, etc of the software. It is performed by the Specialized QA testers or engineers. 

For example,

• Does the site load under 2 seconds with 1000 users?
• Is the data entered by the user protected?

3. Regression Testing

Regression Testing focuses on features that the software works correctly, after changes and bugs are fixed in the software. It runs the test cases that were previously written and checks if the new changes have caused any unexpected issues.

It can be manual for the small projects and automatic for the large projects. It is essential in agile development of the software, and is performed by the QA testers or automation engineers.

For example, after adding a new payment method in a software:

• Test if the existing checkout process works correctly
• Ensure that the old payment options still function correctly.

Note: Regression testing can be black box if the testers only test external behaviour, not internal code changes.

Ways of Black Box Testing Done

There are many ways to perform black box testing. Some of the ways are:

1. Syntax-Driven Testing

In this testing, the system follows some grammar or rules like a language to test the different cases. Then these test cases are used to check if all the rules are used at least once. It is mainly used in automated testing, which is why it is called a type of functional automation testing. 

2. Equivalence Partitioning

It is also called Equivalence Class Partitioning (ECP). It divides the group into two classes, i.e., valid (correct values) and invalid (incorrect values), based on these groups, the test cases are derived. 

The technique has two steps:

a. Identification of equivalence class: First, look at the input range of the system. Then divide the input into a valid or invalid class. 

b. Generating test cases: First, pick one value from each valid or invalid class to use in testing. Then select at least one value from the class that you have selected above.

3. Boundary Value Analysis

In this, the values are tested at the edges because the chances of error coming at the edges are high.

For example, if the valid range is between 10 and 100, then the values like 9,10, 100, and 101 should also be tested.

4. Cause-Effect Graphing

This method finds the relationship between causes and effects, i.e., input and output

The steps in this way are as follows:

• Find all the inputs and outputs. 
• Draw a graph showing the relationship of how they are connected. 
• Turn the graph into a table. 
• Then write test cases with the help of the table

5. Requirement-Based Testing

This checks if the software meets the given requirements. In this, every test must match a requirement of the software, and it should also make sure that everything is working as expected. It should start testing at an early stage to avoid confusion.

The goal is to make sure the final product does exactly what was asked for. It has the following principles:

• Traceability: Every test case should be linked to a specific requirement, which helps track which part of the software each test is validating.
• Early Involvement: It starts testing as early as possible in the project, which helps to understand the requirements better.
• Improves Quality and Confidence: Since tests are performed as per the requirements, it is easier to find bugs.
• Validation and Verification: 
  • Validation: It checks that we are building the right product 
  • Verification: It checks if we are building the product right.

6. Compatibility Testing

This checks if the software works on different devices and systems. It does not depend on the software, it depends on the product.

For example:

• Different processors (like Pentium 3 or 4)
• Windows, Linux, etc.

What Does Black Box Testing Focus On?

Black Box Testing focuses on the input and output of the software. Here are the main things Black Box Testing focuses on:

1. Functionality: It checks if the software is performing as expected for a specific function it was designed. For example, if you click on the login button, does it actually log you in?

2. Input and Output: The tester gives some input and checks the output as per the expected results. It checks for valid and invalid input and output.

3. User Interface (UI): It checks how the software is visible to the user, like its menu, buttons, etc.

4. Requirements: It checks whether the software meets all the business or user requirements that were defined before development. If the software does not meet the requirements of the user, it is considered incomplete, even if it works technically good

5. Behavior in Different Conditions: It checks how the software behaves with correct data, wrong data, empty fields, large inputs, and unexpected user actions.

6. Error Handling: It checks that the system is showing proper messages when something goes wrong. For example, if the user enters alphabets where only numbers are used, it should give an error.

Features of Black Box Testing

Black Box Testing has many features that make it popular among users. Some of them are:

1. No Need to Know the Code: You do not need to know the whole program code; the tester only sees what the software is doing, not how it is doing it.

2. Tests from the User’s Point of View: The software is tested as if the real user is using it. It helps to identify the real issues in the software that the developer is not able to find.

3. Based on Requirements: You first create test cases using the requirements or features given by the client or product team. For example, if the requirement says that the user should be able to log in, then you have to test if the login works, with the correct and incorrect inputs.

4. Used at Different Levels: Black Box Testing can be done at various levels. For the parts that are working together, integration-level testing can be used, and for the testing of the whole app, system testing can be used, and so on.

5. Good for Testing Big Applications: Black Box Testing is good for software systems that are too large, as the tester does not have to check every line of the code.

6. Helps Find Missing Features: Since you are testing based on requirements, you may be able to find that something important is missing in the software.

7. Tests Both Functional and Non-Functional Things: It tests both functional and non-functional things of the software, i.e., what the software should do and how it performs.

8. Testing is Independent: The person testing the app may be different from the developer, which makes the testing more unbiased and fair.

Now, let us discuss the advantages and disadvantages of the black box testing.

Advantages of Black Box Testing

1. In this type of testing, the tester can do the testing even if he does not know programming.

2. It focuses on the real-world usage of the software and helps improve the user experience.

3. It helps to find the missing features in the software.

Disadvantages of Black Box Testing

1. It has limited test coverage, i.e., cannot test the internal logic or code paths.

2. It is difficult when the logic in the software is complex.

3. If the output is correct, a bug in the code may still be present but not caught.

Black Box vs White Box Testing vs Grey Box Testing

Best Practices for Black Box Testing

1. First, understand the requirements of the software clearly, and then start the testing.

2. Mainly focus on the input values and their expected outputs.

3. The groups with similar inputs should be kept in one set, so that only one value can be tested from each group. Example: For age input (1–100), the value 50 can be checked.

4. Always test at the edge cases of input ranges, for example, in the range test, the starting and ending points of the range must be checked.

5. The tester should think like a real user and test for all the possible test cases that a real user can think of.

6. Write each test case with a clear description, input, expected result, and proper steps, so that others can easily understand or repeat the test.

7. Keep a note of what tests you did on the software, what happened, and any problems you found. This will help you to remember what you have tested and make it easier to test again later.

Tools and Frameworks Used for Black Box Testing

1. Selenium: It is a popular tool used to test if buttons, forms, and links work on a website. It supports many languages like Java, Python, and C#.

2. Katalon Studio: It is an all-in-one testing tool used for web, mobile, and APIs. It has a friendly interface. It is good for quick testing, without doing much coding.

3. TestComplete: It is a commercial tool that allows testing desktop, web, and mobile apps. It is best for teams that need strong test management and support.

4. QTP (now UFT): It is a paid tool by Micro Focus used for testing web and desktop applications. It is often used in large enterprises for detailed functional testing.

5. Postman: It is a tool for testing APIs, how software components talk to each other. In this, you can send requests and check the response of each API easily. It is used when testing the apps that connect to the servers or other services.

6. Cypress: It is a fast-growing tool used for end-to-end testing of web apps. It is great for modern web development and provides fast feedback.

Real-World Examples of Black Box Testing

1. Login Function Test: If a user enters their username and password to log in.

• Input: Username and password.
• Expected Output:
  • If the input is correct, the user logs in.
  • If the input is incorrect, it should show the Invalid credentials message.

2. Online Shopping Cart: A user adds and removes items from a cart on an e-commerce website.

• Input: The user clicks Add to Cart and Remove.
• Expected Output: Cart shows updated total and correct number of items.

3. ATM Machine: A user inserts a card, enters a PIN, and withdraws money.

• Input: A Card, PIN, and amount.
• Expected Output:
  • If the PIN is correct, the withdrawal is successful.
  • If the PIN is incorrect, the error message is displayed.

4. Mobile App Login with OTP: A user logs in using a One-Time Password.

• Input: Mobile number and OTP.
• Expected Output:
  • If the OTP is correct, the login is successful.
  • If the OTP is wrong OTP, an error message is displayed.

5. Form Submission: Filling out a contact form on a website.

• Input: A Name, email, and message.
• Expected Output:
  • Successful submission, thank you message.
  • Missing required field, error shown.

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Conclusion

With this, we have learned that Black Box Testing is a simple way to check if the software works as expected without looking at the code. It focuses on testing what the user sees and does. This helps find bugs and improve quality. Tools like Selenium and Postman make testing easier. It’s a great way to make sure that the software is reliable and user-friendly.

If you want to learn more about this topic, you can refer to our Java course.

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