Black Box Testing Tutorial: A Comprehensive Guide With Examples and Best Practices

Black box testing is a software testing methodology that focuses on the functional requirements of a system without considering its internal workings or implementation details. Therefore, the tester need not have any knowledge of the internal structure or design of the system.

It ensures that a system meets the requirements specified by the customer or user. A black box test can be conducted at different levels, including unit testing, integration testing, and system testing. In order to identify defects and ensure that a system works properly, running black-box tests is a valuable approach.

What Is Black Box Testing?

Black box testing is a software testing method that examines the software without prior knowledge of its internal structure. It can be contrasted with White box testing, which involves a more in-depth knowledge of the software's implementation details.

In theory, Black box tests can be run by anyone, independent of the development team, and a developer's familiarity with the code should not affect how well their code is tested; conversely, White box tests tend to require a developer's intimate understanding of the code to construct test cases.

So the primary job of a software tester while running Black box tests is to test the functionalities of software applications when the internal paths and code structure are unknown.

The customer's set of detailed requirements for the product is tested. These requirements are related to different functions, so a tester chooses a function, enters an input value, and examines the output. If the function's result is correct, it is passed in testing.

It is also sometimes referred to as behavioral testing, as instead of the technical perspective, behaviors are considered from the point of view of a software program in various situations.

Why Should We Perform Black Box or Behavior Testing?

The need is to determine how a software program behaves instead of focusing on the technical aspects under various conditions. It also helps you to identify different errors like:

• Performance errors
• Usability errors
• Functionality errors
• Initializing and terminating errors
• Concurrency and timing problems
• Bridge the communication gap

Advantages of Black Box Testing

This section will discuss some of the benefits of executing Black box tests.

• The way users interact with a product and their overall perception, i.e., tests are performed from the user's point of view. Things like meeting customers' expectations and discrepancies in the specifications are tested.
• Developers and testers work independently to avoid bias.
• Big and complex software systems can be tested more effectively using this method. Therefore, it is especially useful for the testing of large systems.
• Testers do not need technical knowledge or programming skills. They do not need to know IT jargon or how the software has been built.
• Little chance of false positives.
• If a defect is detected early in the testing process, you can correct it easily.

Limitations of Black Box Testing

By definition, Black box tests are done without seeing the inner workings of the application. That said, there are still limitations to what you can accomplish with this method.

• Only a limited number of inputs can be tested, and many program paths will not be checked.
• In many projects, there are no clear specifications. This can make test case design challenging.
• If you don't have technical or programming experience, the risk is that you might not consider all the possible circumstances in your scenario.
• Complete test coverage is impossible.
• It is possible to accelerate the testing process by skipping testing inputs and outputs that are not currently being used.
• If a software designer/developer has already run a test case, additional tests may not be necessary.

Scope of Black Box Testing

Black box tests ensure keeping a check on the input that enters the software while checking the desired output. Below is the scope of Black box tests.

• Test your software easily so that desired use is fulfilled.
• Testers can perform this operation without any coding knowledge of the application.
• It helps examine the functionality of the software.

Types of Black Box Testing

Black box testing is used in three main types of software testing: functional, non-functional, and regression.

Functional Testing

We test the functionality of a software program by specific functions or features of the software. The functional requirements of a system are tested, for example, logging in to an eCommerce site through the correct credentials and also checking through the wrong credentials whether the desired output is obtained.

Non-functional Testing

In non-functional testing, there is a focus on "HOW'. It doesn't test if the features and functions are performed well but focuses on the how part of testing. Non-functional testing is never carried out before functional testing.

Regression Testing

After a fix, upgrade, or other system maintenance, regression testing is done to ensure the new code hasn't adversely affected the existing code. It is used to determine whether a new version of the software performs as well as or better than the previous version. It's possible that a fixed defect could have introduced another defect.

Different Black Box Testing Techniques

Many different Black box test techniques help in testing various features of the software. There are several techniques available out there, but not all of them can be used for every type of application. Some basic techniques are:

Equivalence Partitioning

In this, we need to break up possible inputs into groups and test one example input from each group. An equivalence class is a set of data items considered equivalent to each other, so it will receive the same processing when sent as input to an application.

For example, a food company's software might charge different subscription fees for people who are already members for two years and different for new members. In this case, it is sufficient for testers to check only one case from each group.

Boundary Value Analysis

This technique is closely associated with equivalence class partitioning. A system exhibits a special response at a specific value of an input; that specific response at that specific value is called its boundary. We analyze the application's behavior with test data at the boundaries of equivalence classes.

For example, a specific field may accept only values within that range, like supposing a range is 0 to 100. The tester will see if the system accepts and rejects inputs correctly when the number above is entered.

Decision Tables

Testing the application's behavior based on different combinations of input values is called decision table testing. Many systems provide outputs depending on the conditions in which they are operating. The columns each have a unique combination of elements. Testers can identify the conditions that must be satisfied for a rule to apply, determine the outcome of each rule, and design a test case for each rule. The functions that have a logical relationship between two or more inputs are appropriate.

State Transition Testing

It is a way to determine what the software application does when different values of input are given to the same function. Generally used in cases where there is a transition from one state to another. Like in the case of the login mechanism where after a specific number of failed login attempts, it goes into a transition where the locking of the account takes place.The testers here design test cases that probe the system when it transitions states.

Error Guessing

This technique involves identifying common errors developers make when building similar systems. It's a way to identify errors without setting forth a specific method. Instead, the tester will be guided by experience when trying to find unknown problems in the software here.

Use Case Testing

Use case testing is a form of software testing that uses use cases. As per the usage of the system, they are used to identify the test cases from start to end. A test scenario is created based on the functionality of each function from beginning to end.

Cause-Effect Technique

It's a technique that explains the relationship between a result and all the factors that impact it. Dynamic test cases are used here. This technique also called the cause-effect graph technique, is based on a collection of requirements and is used to determine the minimum number of tests that can cover the maximum number of sections in the software.

The cause-and-effect graph technique can convert the requirements specification into a logical relationship between input and output conditions.

All-pair Testing Technique

It is also known as pairwise testing. It is used to test all the possible combinations of values. The applications that use checkbox input, radio button input, list box, and text box use this combinatorial method.

Tools to Perform Black Box Testing

With so many options to choose from, it can be hard to find the right tools you need to test applications. Here are some of the most common tools:

Selenium 

Selenium is a browser automation tool that lets you write scripts in the programming language of your choice. Selenium provides a variety of drivers to support almost all web browsers., and it lets you perform different actions in each browser.

Appium

Appium is a community-driven open-source project that's developing an open standard for automated testing of mobile websites and apps. It is a cross-platform testing framework, supporting both Android and iOS native apps and websites accessed through mobile browsers.

LoadRunner 

LoadRunner, from Micro Focus, is a testing tool that measures how applications behave under heavy loads. LoadRunner helps you test mobile apps by measuring their performance, scalability, and capacity.

JMeter

JMeter is a Java-based load and performance testing tool that works with JDK 5 or higher. It's used to test the performance of Web applications and other types of software under heavy loads.

How to Perform Black Box Testing?

In this section, let's look at how to run your Black box tests.

• Determine and understand the software application's requirements and specifications.
• Check valid and invalid inputs along with expected outputs to validate that the system identifies them appropriately.
• Create automated test cases with multiple test scenarios and inputs.
• Run the test cases.
• Validate the desired results with the actual results.
• Resolve test case errors.
• After, re-test the application to avoid recurring bugs.

While performing testing, you must also take different browsers, browser versions, devices, and operating systems into account. It ensures your software applications work perfectly across each configuration.

Instead of procuring every browser, device, and OS for your target audience, consider using a cloud-based testing infrastructure.

White Box vs. Black Box Testing: Differences

Let's look at the differences between Black box and White box testing.

Conclusion

In this guide, we have covered some of the main points regarding Black box testing, its advantages, and disadvantages, so you can decide in what situations you should do it.