Chapter 2

Unit 2: Types and Levels of Testing
Course Co-ordinator: Mrs. Kshirsagar S.R. M.M.Polytechnic , Thergaon Page 1
CO2 : Prepare test cases for different types and levels of testing.
Levels of Testing
Unit Testing
 Unit Testing is a level of software testing where individual units/ components of a
software are tested. The purpose is to validate that each unit of the software performs as
designed.
 Unit Testing is the first level of testing and is performed prior to Integration Testing.
 A unit is the smallest testable part of software. It usually has one or a few inputs and
usually a single output.
 It is executed by the Developer.
 Unit Testing is performed by using the White Box Testing method
 Example: - A function, method, Loop or statement in program is working fine.

Drivers
 Drivers are used in bottom-up integration testing approach.
 It can simulate the behavior of upper-level module that is not integrated yet.
 Drivers modules act as the temporary replacement of module and act as the actual
products.
 Drivers are also used for interact with external system and usually complex than stubs.
 Driver: Calls the Module to be tested.
Now suppose you have modules B and C ready but module A which calls functions from
module B and C is not ready so developer will write a dummy piece of code for module A
which will return values to module B and C. This dummy piece of code is known as driver.
Stubs
 Stubs are used in top down integration testing.
 It can simulate the behavior of lower-level module that are not integrated.
 They are act as a temporary replacement of module and provide same output as actual
product.
 When needs to intact with external system then also stubs are used.
 Stub: Is called by the Module under Test.
Assume you have 3 modules, Module A, Module B and module C. Module A is ready and
we need to test it, but module A calls functions from Module B and C which are not ready, so
developer will write a dummy module which simulates B and C and returns values to module
A. This dummy module code is known as stub.
Importance of Stubs and Drivers

1. Stubs and Drivers works as a substitute for the missing or unavailable module.
2. They are specifically developed, for each module, having different functionalities.
3. Generally, developers and unit testers are involved in the development of stubs and
drivers.
4. Their most common use may be seen in the integration incremental testing, where stubs
are used in top bottom approach and drivers in a bottom up approach.
Benefits of Unit Testing
 Unit testing increases confidence in changing/ maintaining code. If good unit tests are
written and if they are run every time any code is changed, we will be able to promptly
catch any defects introduced due to the change.
 Codes are more reusable.
 Development is faster.
 The cost of fixing a defect detected during unit testing is lesser in comparison to that of
defects detected at higher levels.
 Debugging is easy.
Integration Testing
 Integration Testing is a level of software testing where individual units are combined and
tested as a group.
 In integration Testing, individual software modules are integrated logically and tested as
a group.

 Integration testing tests integration or interfaces between components, interactions to
different parts of the system such as an operating system, file system and hardware or
interfaces between systems.
 As displayed in the image below when two different modules ‘Module A’ and ‘Module
B’ are integrated then the integration testing is done.
1. Incremental Approach:
 In this approach, testing is done by joining two or more modules that are logically
related. Then the other related modules are added and tested for the proper functioning.
Process continues until all of the modules are joined and tested successfully.
 This process is carried out by using dummy programs called Stubs and Drivers. Stubs and
Drivers do not implement the entire programming logic of the software module but just
simulate data communication with the calling module.
 Stub: Is called by the Module under Test.
 Driver: Calls the Module to be tested.
2. Non- Incremental Integration
 . The non-incremental approach is also known as ―Big-Bang‖ Testing.
 Big Bang Integration Testing is an integration testing strategy wherein all units are
linked at once, resulting in a complete system.
 When this type of testing strategy is adopted, it is difficult to isolate any errors found,
because attention is not paid to verifying the interfaces across individual units.
 In Big Bang integration testing all components or modules are integrated simultaneously,
after which everything is tested as a whole. As per the below image all the modules from
‘Module 1’ to ‘Module 6’ are integrated simultaneously then the testing is carried out.

3. Top down Integration
The strategy in top-down integration is look at the design hierarchy from top to bottom. Start
with the high - level modules and move downward through the design hierarchy. In this approach
testing is conducted from main module to sub module. If the sub module is not developed a
temporary program called STUB is used for simulate the sub module. Modules subordinate to the
top modules are integrated in the following two ways:
1. Depth first Integration: In this type, all modules on major control path of the design
hierarchy are integrated first. In this example shown in fig. modules 1, 2, 4/5 will be integrated
first. Next, modules 1, 3, 6 will be integrated.
2. Breadth first Integration: In this type, all modules directly subordinate at each level, moving
across the design hierarchy horizontally, are integrated first. In the example shown in figure
modules 2 and 3 will be integrated first. Next, modules 4,5 and 6 will be integrated .
Procedure:
The procedure for Top-Down integration process is discussed in the following steps:
1. Start with the top or initial module in the software. Substitute the stubs for all the subordinate
of the top module. Test the top module.
2. After testing the top module, stubs are replaced one at a time with the actual modules for
integration.
3. Perform testing on this recent integrated environment.
4. Regression testing may be conducted to ensure that new errors have not appeared.
5. Repeat steps 2-4 for whole design hierarchy.
Advantages:
 Advantageous if major flaws occur toward the top of the program.
 Once the I/O functions are added, representation of test cases is easier.
 Early skeletal Program allows demonstrations and boosts morale.
Disadvantages:

 Stub modules must be produced
 Stub Modules are often more complicated than they first appear to be.
 Before the I/O functions are added, representation of test cases in stubs can be difficult.
 Test conditions may be impossible, or very difficult, to create.
 Observation of test output is more difficult.
 Allows one to think that design and testing can be overlapped.
 Induces one to defer completion of the testing of certain modules.
4. Bottom up Integration
In this approach testing is conducted from sub module to main module, if the main module is not
developed a temporary program called DRIVERS is used to simulate the main module.
Advantages:
 Advantageous if major flaws occur toward the bottom of the program.
 Test conditions are easier to create.
 Observation of test results is easier.
 Driver Modules must be produced.
 The program as an entity does not exist until the last module is added
Disadvantages:

 Critical modules (at the top level of software architecture) which control the flow of
application are tested last and may be prone to defects.
 Early prototype is not possible
5. Bi Direction / Sandwich Integration Testing
1. Bi-directional Integration is a kind of integration testing process that combines top-down
and bottom-up testing.
2. With an experience in delivering Bi-directional testing projects custom software
development services provide the best quality of the deliverables right from the development
of software process.
3. Bi-directional Integration testing is a vertical incremental testing strategy that tests the
bottom layers and top layers and tests the integrated system in the computer software
development process.
4. Using stubs, it tests the user interface in isolation as well as tests the very lowest level
functions using drivers.
5. Bi-directional Integration testing combines bottom-up and top-down testing.
6. Bottom-up testing is a process where lower level modules are integrated and then tested.
7. This process is repeated until the component of the top of the hierarchy is analyzed. It
helps custom software development services find bugs easily without any problems.
8. Top down testing is a process where the top integrated modules are tested and the
procedure is continued till the end of the related module.
9. Top down testing helps developers find the missing branch link easily

10. This technique is called as Sandwich Integration.
Advantages:
1. Sandwich approach is useful for very large projects having several subprojects.
2. Both Top-down and Bottom-up approach starts at a time as per development schedule.
3. Units are tested and brought together to make a system Integration is done downwards.
Disadvantages:
1. It require very high cost for testing because one part has Top-down approach while another
part has bottom-up approach.
2. It cannot be used for smaller system with huge interdependence between different modules. It
makes sense when the individual subsystem is as good as complete system.
Unit test Integration test
 The idea behind Unit Testing is to test
each part of the program and show that
the individual parts are correct.
 The idea behind Integration Testing is to
combine modules in the application and
test as a group to see that they are
working fine
 It is kind of White Box Testing  It is kind of Black Box Testing
 It can be performed at any time  It usually carried out after Unit Testing
and before System Testing
 Unit Testing tests only the functionality
of the units themselves and may not
catch integration errors, or other
system-wide issues
 Integrating testing may detect errors
when modules are integrated to build the
overall system
 It starts with the module specification  It starts with the interface specification
 It pays attention to the behavior of
single modules
 It pays attention to integration among
modules
 Unit test does not verify whether your
code works with external dependencies
 Integration tests verify that your code
works with external dependencies

correctly. correctly.
 It is usually executed by the developer  It is usually executed by a test team
 Finding errors is easy  Finding errors is difficult
 Maintenance of unit test is cheap  Maintenance of integration test is
expensive
Performance Testing
 Performance Testing is a type of testing to ensure software applications will perform well
under their expected workload.
 A software application's performance like its response time, reliability, resource usage
and scalability do matter.
 The goal of Performance Testing is not to find bugs but to eliminate performance
bottlenecks.
 The focus of Performance Testing is checking a software program's
 Speed - Determines whether the application responds quickly
 Scalability - Determines maximum user load the software application can handle.
 Stability - Determines if the application is stable under varying loads
Test objectives frequently include the following:
 Response time. For example, the product catalog must be displayed in less than
3 seconds.
 Throughput. For example, the system must support 100 transactions per second.
 Resource utilization. A frequently overlooked aspect is the amount of resources
your application is consuming, in terms of processor, memory, disk input output
(I/O), and network I/O.
1. Load Testing
 Load Testing is type of performance testing to check system with constantly increasing
the load on the system until the time load is reaches to its threshold value.

 Here Increasing load means increasing number of concurrent users, transactions & check
the behavior of application under test.
 It is normally carried out underneath controlled environment in order to distinguish
between two different systems.
 The main purpose of load testing is to monitor the response time and staying power of
application when system is performing well under heavy load.
 The successfully executed load testing is only if the specified test cases are executed
without any error in allocated time.
 Load testing is testing the software under customer expected load.
 In order to perform load testing on the software you feed it all that it can handle. Operate
the software with largest possible data files.
 If the software operates on peripherals such as printer, or communication ports, connect
as many as you can.
 If you are testing an internet server that can handle thousands of simultaneous
connections, do it. With most software it is important for it to run over long periods.
 Some software‘s should be able to run forever without being restarted. So Time acts as a
important variable.
 Load testing can be best applied with the help of automation tools..
Simple examples of load testing:
 Testing printer by sending large job.
 Editing a very large document for testing of word processor
 Continuously reading and writing data into hard disk.
 Running multiple applications simultaneously on server.
 Testing of mail server by accessing thousands of mailboxes
 In case of zero-volume testing & system fed with zero load
2. Stress Testing
 Stress Testing is performance testing type to check the stability of software when
hardware resources are not sufficient like CPU, memory, disk space etc.
 It is performed to find the upper limit capacity of the system and also to determine how
the system performs if the current load goes well above the expected maximum.
 Main parameters to focus during Stress testing are “Response Time” and “Throughput”.
 Stress testing is Negative testing where we load the software with large number of
concurrent users/processes which cannot be handled by the systems hardware resources.
This testing is also known as Fatigue testing
 Stress testing is testing the software under less than ideal conditions. So subject your
software to low memory, low disk space, slow cps, and slow modems and so on. Look at
your software and determine what external resources and dependencies it has.

 Stress testing is simply limiting them to bare minimum. With stress testing you starve the
software.
 For e.g. Word processor software running on your computer with all available memory
and disk space, it works fine. But if the system runs low on resources you had a greater
potential to expect a bug. Setting the values to zero or near zero will make the software
execute different path as it attempt to handle the tight constraint. Ideally the software
would run without crashing or losing data
3. Security Testing
 Security testing is a testing technique to determine if an information system protects data
and maintains functionality as intended
 It also aims at verifying 6 basic principles as listed below:
 Confidentiality
 Integrity
 Authentication
 Authorization
 Availability
 Non-repudiation
 Confidentiality
A security measure which protects against the disclosure of information to parties other than the
intended recipient is by no means the only way of ensuring the security.
 Integrity
Integrity of information refers to protecting information from being modified by unauthorized
parties
 Authentication
This might involve confirming the identity of a person, tracing the origins of an artifact, ensuring
that a product is what its packaging and labeling claims to be, or assuring that a computer
program is a trusted one
 Authorization
The process of determining that a requester is allowed to receive a service or perform an
operation. Access control is an example of authorization.
 Availability
Assuring information and communications services will be ready for use when expected.
Information must be kept available to authorized persons when they need it.
 Non-repudiation (acknowledgment)
In reference to digital security, non-repudiation means to ensure that a transferred message has
been sent and received by the parties claiming to have sent and received the message. Non-
repudiation is a way to guarantee that the sender of a message cannot later deny having sent the
message and that the recipient cannot deny having received the message.
Example :

 A Student Management System is insecure if ‘Admission’ branch can edit the data of
‘Exam’ branch
 An ERP system is not secure if DEO (data entry operator) can generate ‘Reports’
 An online Shopping Mall has no security if customer’s Credit Card Detail is not
encrypted
 A custom software possess inadequate security if an SQL query retrieves actual
passwords of its users
4. Client Server Testing
i) This type of testing usually done for 2 tier applications (usually developed for LAN) Here we
will be having front-end and backend.
ii) The application launched on front-end will be having forms and reports which will be
monitoring and manipulating data. E.g: applications developed in VB, VC++, Core Java, C,
C++, D2K, Power Builder etc.
iii) The backend for these applications would be MS Access, SQL Server, Oracle, Sybase,
MySQL, Quadbase.
iv) The tests performed on these types of applications would be– User interface testing Manual
support testing– Functionality testing– Compatibility testing & configuration testing –
Intersystem testing.
The approaches used for client server testing are
1. User interface testing: User interface testing, a testing technique used to identify the presence
of defects is a product/software under test by using Graphical user interface [GUI].GUI Testing -
Characteristics:
i) GUI is a hierarchical, graphical front end to the application, contains graphical objects with a
set of properties.
ii) During execution, the values of the properties of each objects of a GUI define the GUI state.
iii)It has capabilities to exercise GUI events like key press/mouse click.
iv) Able to provide inputs to the GUI Objects.
v) To check the GUI representations to see if they are consistent with the expected ones.
vi) It strongly depends on the used technology.
2. Manual testing: Manual testing is a testing process that is carried out manually to find defects
without the usage of tools or automation scripting. A test plan document is prepared that acts as a
guide to the testing process to have the complete test coverage. Following are the testing
techniques that are performed manually during the test life cycle are Acceptance Testing, White
Box Testing, Black Box Testing, Unit Testing, System Testing, Integration Testing.
3. Functional testing: Functional Testing is a testing technique that is used to test the
features/functionality of the system or Software, should cover all the scenarios including failure
paths and boundary cases.
There are two major Functional Testing techniques as shown below:

4. Compatibility testing: Compatibility testing is a non-functional testing conducted on the
application to evaluate the application's compatibility within different environments. It can be of
two types - forward compatibility testing and backward compatibility testing.
1. Forward Compatibility Testing: This type of testing verifies that the software is
compatible with the newer or upcoming versions, and is thus named as forward
compatible.
2. Backward Compatibility Testing: This type of testing helps to check whether the
application designed using the latest version of an environment also works seamlessly in
an older version. It is the testing performed to check the behavior of the
hardware/software with the older versions of the hardware/software.
Operating system Compatibility Testing - Linux , Mac OS, Windows
Database Compatibility Testing - Oracle SQL Server
Browser Compatibility Testing - IE , Chrome, Firefox
Other System Software - Web server, networking/ messaging tool, etc.
Acceptance Testing
 Acceptance Testing is a level of the software testing where a system is tested for
acceptability.

 The purpose of this test is to evaluate the system’s compliance with the business
requirements and assess whether it is acceptable for delivery.
 Usually, Black Box Testing method is used in Acceptance Testing.
 Acceptance Testing is performed after System Testing and before making the system
available for actual use.
 The acceptance test cases are executed against the test data or using an acceptance test
script and then the results are compared with the expected ones.
 The goal of acceptance testing is to establish confidence in the system.
 Acceptance testing is most often focused on a validation type testing.
Acceptance Criteria
Acceptance criteria are defined on the basis of the following attributes
 Functional Correctness and Completeness
 Data Integrity
 Data Conversion
 Usability
 Performance
 Timeliness
 Confidentiality and Availability
 Install ability and Upgradability
 Scalability
 Documentation
Types Of Acceptance Testing
 User Acceptance test
 Operational Acceptance test
 Contract Acceptance testing
 Compliance acceptance testing

 User Acceptance test
It focuses mainly on the functionality thereby validating the fitness-for-use of the system by
the business user. The user acceptance test is performed by the users and application managers.
 Operational Acceptance test
Also known as Production acceptance test validates whether the system meets the requirements
for operation. In most of the organization the operational acceptance test is performed by the
system administration before the system is released. The operational acceptance test may include
testing of backup/restore, disaster recovery, maintenance tasks and periodic check of security
vulnerabilities.
 Contract Acceptance testing
It is performed against the contract’s acceptance criteria for producing custom developed
software. Acceptance should be formally defined when the contract is agreed.
 Compliance acceptance testing
It is also known as regulation acceptance testing is performed against the regulations which must
be adhered to, such as governmental, legal or safety regulations.
Advantages Of Acceptance Testing
 The functions and features to be tested are known.
 The details of the tests are known and can be measured.
 The tests can be automated, which permits regression testing.
 The progress of the tests can be measured and monitored.
 The acceptability criteria are known.
Disadvantages Of Acceptance Testing
 Requires significant resources and planning.
 The tests may be a re-implementation of system tests.
It may not uncover subjective defects in the software, since you are only looking for defects you
expect to find
Alpha Testing

 Alpha Testing is a type of testing conducted by a team of highly skilled testers at
development site. Minor design changes can still be made as a result of alpha testing.
 For Alpha Testing there is a dedicated test team.
 Alpha testing is final testing before the software is released to the general public. It has
two phases:
 In the first phase of alpha testing, the software is tested by in-house developers. They
use either debugger software, or hardware-assisted debuggers. The goal is to catch bugs
quickly.
 In the second phase of alpha testing, the software is handed over to the software QA
staff, for additional testing in an environment that is similar to the intended use.
 Pros Of Alpha Testing
• Helps to uncover bugs that were not found during previous testing activities
• Better view of product usage and reliability
• Analyze possible risks during and after launch of the product
• Helps to be prepared for future customer support
• Helps to build customer faith on the product
• Maintenance Cost reduction as the bugs are identified and fixed before Beta /
Production launch
• Easy Test Management
 Cons Of Alpha Testing
 Not all the functionality of the product is expected to be tested
 Only Business requirements are scoped
Beta Testing
 Beta Testing is also known as field testing. It takes place at customer’s site. It sends the
system/software to users who install it and use it under real-world working conditions.
 A beta test is the second phase of software testing in which a sampling of the intended
audience tries the product out
 The goal of beta testing is to place your application in the hands of real users outside of
your own engineering team to discover any flaws or issues from the user’s perspective
that you would not want to have in your final, released version of the application.
Beta testing can be considered “pre-release testing.

Advantages of beta testing
 You have the opportunity to get your application into the hands of users prior to releasing
it to the general public.
 Users can install, test your application, and send feedback to you during this beta testing
period.
 Your beta testers can discover issues with your application that you may have not
noticed, such as confusing application flow, and even crashes.
 Using the feedback you get from these users, you can fix problems before it is released to
the general public.
 The more issues you fix that solve real user problems, the higher the quality of your
application when you release it to the general public.
 Having a higher-quality application when you release to the general public will increase
customer satisfaction.
 These users, who are early adopters of your application, will generate excitement about
your application.
Sr.No. Alpha testing Beta testing
1
Performed at developer’s site Performed at end user’s site
2
Performed in controlled environment in
developers presence
Performed in uncontrolled environment in
developers absence
3
Less probability of finding errors as it is driven
by developer
High probability of finding errors as it is
used by end user.
4
It is done during implementation phase of
software
It is done at the pre-release of the software
5
It is not considered as live application of
software
It is considered as a live application of the
software.
6
Less time consuming as developer can make
necessary changes in given time
More time consuming as user has to report
the bugs if any via appropriate channels.
7
Alpha testing involves both white box and
black box testing
Beta testing typically uses black box
testing only
8
Long execution cycles may be required for
alpha testing
Only a few weeks of execution are
required for beta testing

Special tests
1. Regression Testing
 Regression Testing is defined as a type of software testing to confirm that a recent
program or code change has not adversely affected existing features.
 Regression Testing is nothing but full or partial selection of already executed test cases
which are re-executed to ensure existing functionalities work fine.
 This testing is done to make sure that new code changes should not have side effects on
the existing functionalities. It ensures that old code still works once the new code changes
are done.
 Regression Testing is required when there is a
 Change in requirements and code is modified according to the requirement
 New feature is added to the software
 Defect fixing
 Performance issue fix
 Retest All
This is one of the methods for Regression Testing in which all the tests in the existing test
bucket or suite should be re-executed. This is very expensive as it requires huge time and
resources.

 Regression Test Selection
Instead of re-executing the entire test suite, it is better to select part of test suite to be run
Test cases selected can be categorized as 1) Reusable Test Cases 2) Obsolete Test Cases.
Re-usable Test cases can be used in succeeding regression cycles.
Obsolete Test Cases can't be used in succeeding cycles.
 Prioritization of Test Cases
Prioritize the test cases depending on business impact, critical & frequently used
functionalities. Selection of test cases based on priority will greatly reduce the regression
test suite.
Selecting test cases for regression testing
It was found from industry data that good number of the defects reported by customers were due
to last minute bug fixes creating side effects and hence selecting the Test Case for regression
testing is an art and not that easy.
Effective Regression Tests can be done by selecting following test cases –
 Test cases which have frequent defects
 Functionalities which are more visible to the users
 Test cases which verify core features of the product
 Test cases of Functionalities which has undergone more and recent changes
 All Integration Test Cases
 All Complex Test Cases
 Boundary value test cases
 Sample of Successful test cases
 Sample of Failure test cases
 Regression Testing Tools
 If your software undergoes frequent changes, regression testing costs will escalate.

 In such cases, Manual execution of test cases increases test execution time as well
as costs.
 Following are most important tools used for both functional and regression testing:
 Selenium: This is an open source tool used for automating web applications. Selenium
can be used for browser based regression testing.
 Quick Test Professional (QTP): HP Quick Test Professional is automated software
designed to automate functional and regression test cases. It uses VBScript language for
automation. It is a Data driven, Keyword based tool.
 Rational Functional Tester (RFT): IBM's rational functional tester is a Java tool used
to automate the test cases of software applications. This is primarily used for automating
regression test cases and it also integrates with Rational Test Manager.
2. GUI Testing
 There are two types of interfaces for a computer application.
 Command Line Interface is where you type text and computer responds to that command.
 GUI stands for Graphical User Interface where you interact with the computer using
images rather than text.
 GUI testing is the process of testing the system's Graphical User Interface of the
Application Under Test. GUI testing involves checking the screens with the controls like
menus, buttons, icons, and all types of bars - toolbar, menu bar, dialog boxes and
windows, etc.
 GUI is what user sees. A user does not see the source code. The interface is visible to the
user. Especially the focus is on the design structure, images that they are working
properly or not.
 GUI Testing Guidelines
1. Check Screen Validations
2. Verify All Navigations
3. Check usability Conditions
4. Verify Data Integrity
5. Verify the object states
6. vi. Verify the date Field and Numeric Field Formats
 Following are the GUI elements which can be used for interaction between the user and
application:

 In addition to functionality, GUI testing evaluates design elements such as layout, colors, fonts,
font sizes, labels, text boxes, text formatting, captions, buttons, lists, icons, links and content.
GUI testing processes can be either manual or automatic, and are often performed by third -party
companies, rather than developers or end users.
Example: Consider any website like MSBTE, Google, yahoo or any login form or GUI of any
application to be tested. It includes following:
 All colors used for background, control colors, and font color have a major impact on users.
Wrong color combinations and bright colors may increase fatigue of users.
 All words, Fonts, Alignments, scrolling pages up and down, navigations for different
hyperlinks and pages, scrolling reduce usability.
 Error messages and information given to users must be usable to the user. Reports and outputs
produced either on screen or printed should be readable. Also paper size on printer, font, size of
screen should be consider.
 Screen layout in terms of number of instructions to users, number of controls and number of
pages are defined in low level design. More controls on single page and more pages reduce
usability.
 Types of control on a single page are very useful considering usability.
 Number of images on page or moving parts on screen may affect performance. These are high-
priority defects. It has direct relationships with usability testing, look, and feels of an application.
It affects emotions of users and can improve acceptability of an application.
Advantages of GUI Testing:

 Good GUI improves feel and look of the application; it psychologically accepts the application
by the user.
 GUI represents a presentation layer of an application. Good GUI helps an application due to
better experience of the users.
 Consistency of the screen layouts and designs improves usability of an application.
Disadvantages of GUI Testing:
 When number of pages is large and number of controls in a single page is huge.
 Special application testing like those made for blind people or kids below age of five may
need special training for testers.

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