There are different levels
during the process of testing. In this chapter, a brief description is provided
about these levels.
Levels of testing include
different methodologies that can be used while conducting software testing. The
main levels of software testing are:
● Functional Testing
● Non-functional Testing
This is a type of black-box
testing that is based on the specifications of the software that is to be
tested. The application is tested by providing input and then the results are
examined that need to conform to the functionality it was intended for. Functional
testing of a software is conducted on a complete, integrated system to evaluate
the system's compliance with its specified requirements.
There are five steps that are
involved while testing an application for functionality.
|
Steps |
Description |
|
I |
The determination of the
functionality that the intended application is meant to perform. |
|
II |
The creation of test data
based on the specifications of the application. |
|
III |
The output based on the
test data and the specifications of the application. |
|
IV |
The writing of test
scenarios and the execution of test cases. |
|
V |
The comparison of actual
and expected results based on the executed test cases. |
An effective testing practice
will see the above steps applied to the testing policies of every organization
and hence it will make sure that the organization maintains the strictest of
standards when it comes to software quality.
This type of testing is
performed by developers before the setup is handed over to the testing team to
formally execute the test cases. Unit testing is performed by the respective
developers on the individual units of source code assigned areas. The
developers use test data that is different from the test data of the quality
assurance team.
The goal of unit testing is to
isolate each part of the program and show that individual parts are correct in
terms of requirements and functionality.
Testing cannot catch each and
every bug in an application. It is impossible to evaluate every execution path
in every software application. The same is the case with unit testing.
There is a limit to the number
of scenarios and test data that a developer can use to verify a source code.
After having exhausted all the options, there is no choice but to stop unit
testing and merge the code segment with other units.
Integration testing is defined
as the testing of combined parts of an application to determine if they
function correctly. Integration testing can be done in two ways: Bottom-up
integration testing and Top-down integration testing.
|
S.N. |
Integration Testing Method |
|
1 |
Bottom-up integration This testing begins with unit testing,
followed by tests of progressively higher-level combinations of units called
modules or builds. |
|
2 |
Top-down integration In this testing, the highest-level
modules are tested first and progressively, lower-level modules are tested
thereafter. |
In a comprehensive software
development environment, bottom-up testing is usually done first, followed by
top-down testing. The process concludes with multiple tests of the complete
application, preferably in scenarios designed to mimic actual situations.
System testing tests the
system as a whole. Once all the components are integrated, the application as a
whole is tested rigorously to see that it meets the specified Quality
Standards. This type of testing is performed by a specialized testing team.
System testing is important
because of the following reasons:
● System testing is the first step in the
Software Development Life Cycle, where the application is tested as a whole.
● The application is tested thoroughly to
verify that it meets the functional and technical specifications.
● The application is tested in an
environment that is very close to the production environment where the
application will be deployed.
● System testing enables us to test,
verify, and validate both the business requirements as well as the application
architecture.
Whenever a change in a
software application is made, it is quite possible that other areas within the
application have been affected by this change. Regression testing is performed
to verify that a fixed bug hasn't resulted in another functionality or business
rule violation. The intent of regression testing is to ensure that a change,
such as a bug fix should not result in another fault being uncovered in the
application.
Regression testing is
important because of the following reasons:
● Minimize the gaps in testing when an
application with changes made has to be tested.
● Testing the new changes to verify that
the changes made did not affect any other area of the application.
● Mitigates risks when regression testing
is performed on the application.
● Test coverage is increased without
compromising timelines.
● Increase speed to market the product.
This is arguably the most
important type of testing, as it is conducted by the Quality Assurance Team who
will gauge whether the application meets the intended specifications and
satisfies the client’s requirement. The QA team will have a set of pre-written
scenarios and test cases that will be used to test the application.
More ideas will be shared
about the application and more tests can be performed on it to gauge its
accuracy and the reasons why the project was initiated. Acceptance tests are
not only intended to point out simple spelling mistakes, cosmetic errors, or
interface gaps, but also to point out any bugs in the application that will
result in system crashes or major errors in the application.
By performing acceptance tests
on an application, the testing team will deduce how the application will
perform in production. There are also legal and contractual requirements for
acceptance of the system.
This test is the first stage
of testing and will be performed amongst the teams (developer and QA teams).
Unit testing, integration testing and system testing when combined together is
known as alpha testing. During this phase, the following aspects will be tested
in the application:
● Spelling Mistakes
● Broken Links
● Cloudy Directions
● The Application will be tested on
machines with the lowest specification to test loading times and any latency
problems.
This test is performed after
alpha testing has been successfully performed. In beta testing, a sample of the
intended audience tests the application. Beta testing is also known as pre-release
testing. Beta test versions of software are ideally distributed to a wide
audience on the Web, partly to give the program a "real-world" test
and partly to provide a preview of the next release. In this phase, the
audience will be testing the following:
● Users will install, run the application
and send their feedback to the project team.
● Typographical errors, confusing
application flow, and even crashes.
● Getting the feedback, the project team
can fix the problems before releasing the software to the actual users.
● The more issues you fix that solve real
user problems, the higher the quality of your application will be.
● Having a higher-quality application when
you release it to the general public will increase customer satisfaction.
This section is based upon
testing an application from its non-functional attributes. Non-functional
testing involves testing a software from the requirements which are nonfunctional in nature but important such as
performance, security, user interface, etc.
Some of the important and
commonly used non-functional testing types are discussed below.
It is mostly used to identify
any bottlenecks or performance issues rather than finding bugs in a software.
There are different causes that contribute in lowering the performance of a
software:
● Network delay
● Client-side processing
● Database transaction processing
● Load balancing between servers
● Data rendering
Performance testing is
considered as one of the important and mandatory testing type in terms of the
following aspects:
● Speed (i.e. Response Time, data rendering
and accessing)
● Capacity
● Stability
● Scalability
Performance testing can be
either qualitative or quantitative and can be divided into different sub-types
such as Load testing and Stress testing.
It is a process of testing
the behavior of a software by applying
maximum load in terms of software accessing and manipulating large input data.
It can be done at both normal and peak load conditions. This type of testing
identifies the maximum capacity of software and its behavior at
peak time.
Most of the time, load testing
is performed with the help of automated tools such as Load Runner, AppLoader, IBM Rational Performance Tester, Apache JMeter, Silk Performer, Visual Studio Load Test, etc.
Virtual users (VUsers) are defined in the automated testing tool and the
script is executed to verify the load testing for the software. The number of
users can be increased or decreased concurrently or incrementally based upon
the requirements.
Stress testing includes
testing the behavior of a software under
abnormal conditions. For example, it may include taking away some resources or
applying a load beyond the actual load limit.
The aim of stress testing is
to test the software by applying the load to the system and taking over the
resources used by the software to identify the breaking point. This testing can
be performed by testing different scenarios such as:
● Shutdown or restart of network ports
randomly
● Turning the database on or off
● Running different processes that consume
resources such as CPU, memory, server, etc.
Usability testing is a
black-box technique and is used to identify any error(s) and improvements in
the software by observing the users through their usage and operation.
According to Nielsen,
usability can be defined in terms of five factors, i.e. efficiency of use,
learn-ability, memory-ability, errors/safety, and satisfaction. According to
him, the usability of a product will be good and the system is usable if it
possesses the above factors.
Nigel Bevan and Macleod
considered that usability is the quality requirement that can be measured as
the outcome of interactions with a computer system. This requirement can be
fulfilled and the end-user will be satisfied if the intended goals are achieved
effectively with the use of proper resources.
Molich in 2000 stated that a user-friendly
system should fulfill the following five
goals, i.e., easy to Learn, easy to remember, efficient to use, satisfactory to
use, and easy to understand.
In addition to the different
definitions of usability, there are some standards and quality models and
methods that define usability in the form of attributes and sub-attributes such
as ISO-9126, ISO-9241-11, ISO-13407, and IEEE std.610.12, etc.
UI testing involves testing
the Graphical User Interface of the Software. UI testing ensures that the GUI
functions according to the requirements and tested in terms of color, alignment, size, and other properties.
On the other hand, usability
testing ensures a good and user-friendly GUI that can be easily handled. UI
testing can be considered as a sub-part of usability testing.
Security testing involves
testing a software in order to identify any flaws and gaps from security and
vulnerability point of view. Listed below are the main aspects that security
testing should ensure:
● Confidentiality
● Integrity
● Authentication
● Availability
● Authorization
● Non-repudiation
● Software is secure against known and
unknown vulnerabilities
● Software data is secure
● Software is according to all security
regulations
● Input checking and validation
● SQL insertion attacks
● Injection flaws
● Session management issues
● Cross-site scripting attacks
● Buffer overflows vulnerabilities
● Directory traversal attacks
Portability testing includes
testing a software with the aim to ensure its reusability and that it can be
moved from another software as well. Following are the strategies that can be
used for portability testing:
● Transferring an installed software from
one computer to another.
● Building executable (.exe) to run the
software on different platforms.
Portability testing can be
considered as one of the sub-parts of system testing, as this testing type
includes overall testing of a software with respect to its usage over different
environments. Computer hardware, operating systems, and browsers are the major
focus of portability testing. Some of the pre-conditions for portability
testing are as follows:
● Software should be designed and coded, keeping
in mind the portability requirements.
● Unit testing has been performed on the
associated components.
● Integration testing has been performed.
● Test environment has been established.