Software Engineering unit 4

SOFTWARE ENGINEERING
UNIT-4
ABHIMANYU MISHRA
ASSISTANT PROF.(CSE)
JETGI
24/12/16 1Abhimanyu Mishra(CSE) JETGI

 Testing objectives.
 Unit testing.
 Integration testing.
 Acceptance testing.
 Regression testing.
 Testing for performance.
 Top down & bottom up strategies: Test driver and Test stub.
 Test data suit preparation.
 Apha & Beta testing of products.
 Static testing Strategies: Formal Technical Reviews, walkthrough.
 Compliance with design and coding standards.
CONTENTS

Software testing is the process of executing a program with the intension of finding
errors in the code. It is a process of evolution of a system or its parts by manual or
automatic means to verify that it is satisfying specified requirements or not.
 Generally no system design is ever perfect due to communication problem
between user & developer, time constrains, or conceptual mistake by developers.
 The purpose of system testing is to check and find out these errors or faults as
early as possible so losses due to it can be saved.
 Testing is the fundamental of software success.
 System testing makes a logical assumption that if all the parts of the system are
working correctly then system goal will be successfully achieved.
 Testing is not a distinct phase in system development life cycle but should be
applicable throughout all phases.
TESTING OBJECTIVES :

OBJECTIVE OF SOFTWARE TESTING:
i. Software quality improvement- the computer and the software are mainly used for
complex and critical applications and a bug or fault in software causes severe losses.
ii. Verification & Validation- The second main objective of software is to verify the
system and checking its validation. Verification means to test that we are building
the product in right way.
iii. Software reliability estimation- software reliability has important relationship with
many aspects of software development. Its objective is to discover the residual
designing errors before delivery to the customer

Softwa
re
Testers
Reliabil
ity
analysi
s
Designe
r
Test inputs Test data
Test outputs
Continue/ change
procedure
Debug system
Evaluate effectiveness of
fixes
Fig- Role of reliability in software testing

VARIOUS TYPES OF TESTING:
Acceptance
testing
System testing
Integration
testing
Unit testing
Client Needs
Requirements
Design
code

Unit testing focuses verification effort on the smallest unit of software
design the software component or module.
Using the component-level design description as a guide, important
control paths are tested to uncovered errors within the boundary of the
module.
In unit testing individual components are tested to ensure that they are
working properly in the same manner as required.
It is the lowest level of testing of application under test software meet the
requirements.
The main reason for doing unit testing is that:
•The size of single module is small enough that can locate error very easily.
•Due to small size it can be tested in demonstrably in exhaustive fashion.
Unit Testing:

M1
M2
M3
M4
M5
M7 M6
Unit testing

INTEGRATION TESTING:
 Once individuals program component have been tested, they must be integrated
to create a partial or complete system.
 Integrated test should develop during system specification, and this integration
testing should begin as soon as usable versions of some of the system
component are available.
 The primary objective of integration testing is to check the module interface i.e.
way of interaction of module, is not having any kind of errors.
The main integration technique are-
i. Top down integration testing
ii. Bottom up integration testing.

Top down integration testing- In top down integration testing, the top level usually
one controlling component is tested. Then all components called by tested
component are combined in the same way and tested as a large unit. This process
continues until all components are integrated and then whole system have been
completely tested.
Advantages of top down testing:
 Design errors are detected as early as possible, saving development time and costs
because corrections in the module design can be made before their
implementation.
 The characteristics of a software system are evident from the start, which enables
a simple test of the development state and the acceptance by the user.
 The software system can be tested thoroughly from the start with test cases
without providing test environments.
Disadvantages of top down testing:
 Strict top down testing proves extremely difficult because designing usable
surrogate objects can prove very complicated, especially for complex operation.
 Errors in lower hierarchy levels are hard to localize.
TOP DOWN TESTING:

BOTTOM-UP INTEGRATION TESTING:
It is very popular approach of merging the components to test a larger system. In
this method each subsystem at the lower level of system hierarchy is tested
individually first. Then the next component who calls the previously tested ones to
be tested.
Advantages of Bottom-Up integrated testing-
 The bottom-up test method is solid & proven. The objects to be tested are
known in full detail. It is often simpler to define relevant test cases and test
data.
 The bottom- up approach is psychologically more satisfying because the tester
can be certain that the foundations for the test objects have been tested in full
detailed.
Disadvantages of Bottom-up integrated testing-
 The characteristics of the finished product are only known after the completion
of all implementation and testing, which means that design error in the upper
level are detected very late
 Testing individual levels also inflicts high costs for providing a suitable test
environment.

ACCEPTANCE TESTING:
 The purpose of acceptance testing is to confirm that the system meets its
business requirements and to provide confidence that the system is working
properly before it is “hand over” to the customer.
 Acceptance testing is performed by nominated user representatives under
guidance and supervision of testing team and developer.
 During acceptance testing it is very important that there should be an
independent observer of testing process specially when the customer are not
having too much IT knowledge.
 The main way to evaluate the system for acceptance is bench mark test. In
this customer prepare a set of a test cases that represents typical condition
under which the system will operate when actually installed. The customer
evaluate the system performance for each test case.

STRESS TESTING:
 In software testing, stress testing refers to tests that determine the robustness
of software by testing beyond the limits of normal operation. Stress testing is
particularly important for “mission critical” software, but is used for all types
of software.
 Stress tests commonly put a greater emphasis on robustness, availability, and
error handling under a heavy load, then on what would be considered correct
behavior under normal circumstances.
 Stress testing typically involves the independent test team performing the
following testing tasks using the following technique:
i. Test planning
ii. Test reuse
iii. Test design

REGRESSION TESTING:
Testing is used to find out errors in the software due to which it is not working properly. When
these errors are found out then different methods are used to correct these errors. But while,
removing process of current errors, some new faults or errors may be generated. Regression
testing is used to identified these new errors or faults.
Regression testing can be applied in development as well as maintenance phase of software
life cycle. In development phase regression testing is done after correcting the errors found
during the testing of software.
A regression test suit contains three different classes of test cases:
 A representative sample of tests that will exercise all software functions.
 Additional tests that focuses on software functions that are likely to be affected by the
change.
 Test that focuses on the software components that have been changed.

TEST DRIVER & TEST STUB:
“A test driver is a software module or application used to invoke a test and provide
test data, control and monitor execution and execution and reports test outcomes”.
Test driver are used for testing of sub-module in the absence of main control module.
A component driver routine calls a particular component and passes test case to it.
Test stub- Test stubs are specialized implementation of elements used for testing
purpose, which are dummy of a real component. Test stubs are program or
components that have deterministic behavior and are used to interface with sub
system in order to take care of dependencies.
• Basically stubs are used in top down approach.in it the main control module is
tested in the absence of stub-module.

WHITE BOX TESTING:
White box testing is a software testing approach that examines the program
structure and derives test data from the program logic.
 In this approach, test group must have complete knowledge about the internal
structure of the software.
 White box testing is also called “structural testing”.
 Structural testing is usually applied to relatively small program units such as
subroutine or operations associated with objects.
 The white box testing is also known by name of glass box testing, clear box
testing, open-box testing.
 It is a test case design method that uses the control structure of the procedural
design to drive test cases.

Fig- White box approach

BLACK BOX APPROACH:
 In Black-box testing the tester don’t know the internal structure of module, it tests only for
input/output behavior. Black-box testing focuses on the functional requirements of the
software. It enables the software engineer to derive sets of input conditions that will fully
exercise all functional requirements for a program.
 The black box testing is also known by the name of functional testing, exterior testing,
specification testing, data- driven testing and input/output driven.
 The selection of test cases is based on the specification of the test object without
knowledge of its behavior of the test object on erroneous input data.
 In black box test on software design the tester only knows the inputs and what will be
expected outputs and don’t know how the program will arrive at those outputs.

24/12/16 Abhimanyu Mishra(CSE) JETGI 19
Advantage of Black box testing-
 The test is unbiased because the designer and tester are
independent of each other.
 Test is done from the point of view of user not the designer.
 Test cases can be design as soon as specification is
completed.
 For tester there is no need to know any programming
language.
Disadvantage of Black box testing-
 The test can be redundant if software designer has already run a test
case.
 The test cases are difficult to design.

Fig- Black box testing

24/12/16 Abhimanyu Mishra(CSE) JETGI 21
TEST DATA SUIT PREPARATION:
Testing is the process of executing a program to locate undiscovered errors. The
main aim of program testing is to identify all defects in a program. However, it
is not possible to guarantee that a program is error free.
Following activities are to be performed during testing process-
 Designing test suit
 Running test cases & checking result
 Debugging
 Error correction

FORMAL TECHNICAL REVIEW:
A formal technical review are filter or software engineering process i.e. review
are applied at various points during software development and serve to
uncover the errors and defects that can be removed. Software reviews
“purifies” the software engineering activities that we have called analysis,
design and coding.
 It is a software quality that assurance activity performed by software
engineers. A FTR is known as WALKTHROUGH or an INSPECTION.
The objective of FTR are:-
 To uncover errors in function, logic or implementation for representation of
software.
 To verify that software under review meets its requirements.
 To ensure that the software has been represented according to predefined
standards.
 To achieve software that is developed in a uniform manner.

DESIGNING & CODING STANDARDS:
Coding standards are a set of conventions that the programmer follow to
standardize their computer code to some degree and to make the overall program
easier to read and understand.
In other words coding standard as it is sometime called is about how you code so
that the code is easily readable and understandable by a human.
 Coding
 Program Robustness
 I/O Behavior
 Modules & Modular program structure
 Program Testing
 Cohesion Procedure
 Minimize coupling
 Minimize data scope where possible

Software Engineering unit 4

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