In a black box, we cannot look through the box to know what is inside; we only know from the outside that it is a black-colored box.

1. Understanding Black Box Testing – Types,
Techniques, and Examples
Introduction
What comes to your mind when you hear the term Black box, specifically concerning
testing? Well, it is something that is not very common to listen to but remains an
essential form of software testing. So, it is a software testing technique to examine
the functioning of software from an external outlook without digging deeper into its
code. The best thing about Black box testing is that it can be applied to all levels of
testing ( Unit, integration, system, and acceptance). Anybody with minimum or no
coding language can perform Black box testing of a software product, software
testers with no coding language can also do it.
What is Black Box Testing?
In a black box, we cannot look through the box to know what is inside; we only know
from the outside that it is a black-colored box. Similarly, in the software testing field,
Black Box testing is a testing technique to examine the application under test without
stressing its design and internal coding structure. It is performed to inspect the
behavior of the software from the outside. Hence, it is also called behavioral testing,
i.e., how your software behaves under different situations without looking at the

2. details of the code. In some or the other way, we all have tried Black Box testing in
our lives. For example, while pressing the start button of a bike, we expect it to start
without getting into its inner working mechanism.
In other words, it focuses on the functionality of the software without any need for
coding knowledge. It includes software testing from the customer’s point of view, the
user interface of the software. It examines the product-customer relationship,
performed to find out the external factors that impact the success or the failure of the
software. Black Box testing is done at the final stages of the testing process to
examine the functional aspects of the software. It focuses only on the input and the
output of the application.
Black box testing helps testers identify the following issues:
– Missing functions of the software
– Errors occurring while using the application interface
– Errors while accessing the database
– Errors occurring during the start and end of a particular function
– Issues in application performance and behavior

3. Black box testing tests the application, keeping the end-user in mind. It checks
the usability, functionality, and the performance of the application as a complete
system.
White box vs. Black box testing
White box testing, in contrast, is a testing methodology purely focused on the
working of the internal code structure of the software. It requires an in-depth
knowledge of coding to understand the way the software is built. Black box testing is
not an alternative for White box testing. It is complementary to it. For example, if you
are making a transaction on the website and testing if any faults occur while
transacting, it is identified with the help of Black box testing. Whereas, if you look into
the source code of the same website to check the functioning of a particular form,
understand the variables, restrictions based on core coding knowledge, it is called
White box testing. In other words, white box testing provides an internal perspective
of the overall system, it checks the design and internal structure of an application
using supreme programming skills.
Examples of Black box testing
Let’s have a look at a couple of examples of Black box testing to have a better
understanding of this testing methodology.
Example 1: Testing if the word processor is working as expected. One scenario is to
examine if the user can create a new file, save, open, or delete the existing file.
Another scenario could be testing the functioning of editing tools like cut, copy,
select, change font size/color of the document, etc.
Example 2: Testing Login Function of a website login screen. With the help of Black
box testing, the tester will test if using a username and password (input) allows one
to login seamlessly to the system (output). Here, the tester will not get into the

4. function of the code behind it; he will just check the validity of the input given and the
outcome received. If the user feeds a wrong password and does not get any error
message, black box testers detect this and send it to the coders for resolution.
There are different approaches to execute Black box testing, like:
–Manually: By testing user data and error messages, check the UI of the application
as a user.
–Automatic: It records the user interaction with the software to figure out errors
–Documentation: A type of manual approach in which the tester documents the
functions that the software should perform without focusing on how it should perform
them.
Types of Black box testing
With its growing scope, Black box testing has many types, out of which the
prominent and most preferred ones are:
Functional Testing: It is the most commonly used type of black box testing in which
the tester focuses on the core functionality, operations, and specifications of the
software. Testers perform it by feeding input to the application for getting the desired
output. It is usually performed before non-functional testing. Various types of
functional testing are Smoke, Unit, Integration, User acceptance testing, etc., and
can be performed either in a manual or automated way.
Non-Functional Testing: This type of Black box testing focuses on aspects other
than functionality of the software like usability, reliability, scalability, and
performance. Any issue related to these aspects can critically impact the user
experience. Hence it is necessary to maintain the quality of the product. Various
types of non-functional testing are load, performance, stress, compliance testing, etc.

5. Regression Testing: It is carried out after code fixes/changes or system upgrades
to ensure any code modification should not impact the existing functionalities of the
software. It is an essential part of the SDLC; any software must go through
regression testing to handle unseen implications.
Techniques of Black box testing
We know how impactful and beneficial Black box testing can be to the organization
in improving the quality of its software application. There are many techniques of
Black box testing available for fulfilling software testing requirements. Let’s have a
look at the popular ones to include in the test strategy.
1. Equivalence Partitioning
In this type of Black box testing technique, the inputs that behave homogeneously or
yield similar outcomes are divided and grouped under one category. One input value
from each group is picked and tested. For every group, one representative value is
selected and tested. Testing each value in the group would be time-consuming. In
this technique, only the representative value is tested from each group, making it
easier to test many inputs at once, maintaining test coverage, and reducing rework.
2. Boundary Value Analysis
It is a popular black box testing technique that works on similar lines of equivalence
testing. However, instead of testing the representative value from each group, this
technique tests the boundary value of each input group (including both valid and
invalid inputs). It is observed that applications face problems near the boundary,
which means that the limit after which the system starts behaving differently.
3. Decision Table Testing
This technique is appropriate in conditions where the functionalities have logical input
between them, like if/else conditions. Here different input combinations are
considered. We use conditions (inputs) and actions (outputs) to examine system
behavior using decision tables.

6. 4. State Transition Testing
In this technique, the inputs/outputs and system states are considered in the entire
testing phase. It tests the software application for a sequence of transitions of test
inputs. It checks the system behavior changes depending upon what events have
occurred/ or what input value is given. Events set off states which become scenarios
that the testers test. For example: When a user enters a wrong password thrice, all
three inputs will be sent to the login page. The third attempt will produce an error
message for the user. This method considers all three system states and passes only
the right state sequence.
5. Graph-based testing
A graph is prepared for the objects that the application consists of. Then
based on this object graph, the relationship between each object is figured
out, and a test is written to discover errors. It visualizes the flow and
correlation of inputs and outputs.
6. Error guessing technique:
This testing technique is entirely experience-based. Here, the tester guesses
the erroneous aspects (input/output) of the application. The judgment is solely
based on his previous experience with the software behavior, functionalities,
and impacts on end-user experience.
Apart from the above-stated techniques of black box testing, there are a few more,
such as all pair testing and orthogonal array testing, comparison testing, etc.
Conclusion
To ensure that the software quality is maintained and you do not lose customers
because of a bad user-experience, your application should go through stern
supervision using suitable testing techniques. Black box testing is the easiest and

7. fastest solution to investigate the software functionalities without any coding
knowledge. The debate on white box vs. black box testing is an ever-prevailing
discussion, where both stand out as winners. Whether you want White box testing or
Black box testing depends upon how deeper you want to get into the software
structure under test. If you want to test the functionalities with an end-user
perspective, Black box testing fits the bill. And, if you wish to direct your testing
efforts towards how the software is built, its coding structure, and design, then white
box testing works well. However, both aim to improve the software quality in their
own different ways. There are a lot of black box testing techniques discussed above.
A tester can combine different techniques to reap the benefits of black box testing.
Whatever testing method you use, the ultimate aim of your testing strategy should be
to minimize errors and the risks of app failure and maximize software quality and
user experience.