Unit testing validates that individual software units perform as designed by testing them in isolation from the rest of the system using stubs and drivers. Integration testing exposes faults in interactions between integrated units by combining and testing them as a group. System testing evaluates the integrated system's compliance with requirements by testing the complete system.

3.  DEFINITION
 Unit Testing is a level of the software
testing process where individual
units/components of a software/system
are tested.
 The purpose is to validate that each unit
of the software performs as designed.

4.  A unit is the smallest testable part of
software. It usually has one or a few
inputs and usually a single output.
 For example, In procedural
programming a unit may be an
individual
program, function, procedure, etc. In
object-oriented programming, the
smallest unit is a method, which may
belong to a base/super class, abstract
class or derived/child class.

6.  Component testing may be done in
isolation from the rest of the system
depending on the context of the
development life cycle and the system.
 Most often stubs and drivers are used to
replace the missing software and
simulate the interface between the
software components in a simple
manner.
 A stub is called from the software
component to be tested; a driver calls a
component to be tested.

7.  METHOD
 Unit Testing is performed by using
the White Box Testing method.
 UNIT TEST PLAN
 Prepare
 Review
 Rework
 Baseline

8.  When is it performed?
 Unit Testing is the first level of testing and
is performed prior to Integration Testing.
 Who performs it?
 Unit Testing is normally performed by
software developers themselves or their
peers. In rare cases it may also be
performed by independent software
testers.

9.  DEFINITION
 Integration Testing tests interfaces between
computers, interactions to different parts of
a system such as an OS, file system and
hardware or interfaces between systems.
 Integration Testing is a level of the software
testing process where individual units are
combined and tested as a group.
 The purpose of this level of testing is to
expose faults in the interaction between
integrated units.

10.  EXAMPLE
 During the process of manufacturing a
ballpoint pen, the cap, the body, the tail
and clip, the ink cartridge and the
ballpoint are produced separately and
unit tested separately.
 When two or more units are ready, they
are assembled and Integration Testing is
performed. For example, whether the
cap fits into the body or not.

11.  METHOD
 Any of Black Box Testing, White Box
Testing, and Gray Box Testing methods
can be used. Normally, the method
depends on your definition of ‘unit’.
 INTEGRATION TEST PLAN
 Prepare
 Review
 Rework
 Baseline

12.  When is Integration Testing performed?
 Integration Testing is performed after Unit
Testing and before System Testing.
 Who performs Integration Testing?
 Either Developers themselves or
independent Testers perform Integration
Testing.

13.  Top-down Approach
 Top down approach tests the
integration from top to bottom, it
follows the architectural structure.
 Example: Integration can start
with GUI and the missing
components will be substituted by
stubs and integration will go on.

14.  Bottom-up approach
 In bottom up approach testing takes
place from the bottom of the control
flow, the higher level components are
substituted with drivers
 Big bang approach
 In big bang approach most or all of
the developed modules are coupled
together to form a complete system
and then used for integration testing.

15.  DEFINITION
 System Testing is a level of the software
testing process where a
complete, integrated system/software is
tested.
 The purpose of this test is to evaluate the
system’s compliance with the specified
requirements.

16.  EXAMPLE
 During the process of manufacturing a
ballpoint pen, the cap, the body, the
tail, the ink cartridge and the ballpoint
are produced separately and unit tested
separately.
 When two or more units are ready, they
are assembled and Integration Testing is
performed. When the complete pen is
integrated, System Testing is performed.

17.  METHOD
 Usually, Black Box Testing method is used.
 SYSTEM TEST PLAN
 Prepare
 Review
 Rework
 Baseline

18.  When is it performed?
 System Testing is performed
after Integration Testing and
before Acceptance Testing.
 Who performs it?
 Normally, independent Testers perform
System Testing.

19.  DEFINITION
 Acceptance testing is performed after system
testing is done and all or most of the major
defects have been fixed.
 The goal of acceptance testing is to establish
confidence in the delivered software/system
that it meets the end user/customers
requirements and is fit for use Acceptance
testing is done by user/customer and some of
the project stakeholders.
 Acceptance testing is done in production kind
of environment.

20.  For Commercial off the shelf (COTS)
software’s that are meant for the mass
market testing needs to be done by the
potential users, there are two types of
acceptance testing for COTS software’s.
• Alpha Testing
• Beta Testing

21.  Alpha Testing
 Alpha testing is mostly applicable for
software’s developed for mass market
i.e. Commercial off the
shelf(COTS), feedback is needed from
potential users.
 Alpha testing is conducted at
developers site, potential users, members
or developers organization are invited to
use the system and report defects.

22.  Beta Testing
 Beta testing is also know as field testing, it
is done by potential or existing
users/customers at an external site
without developers involvement.
 This test is done to determine that the
software satisfies the end users/
customer’s needs. This testing is done to
acquire feedback from the market.