Software Engineering-Unit 5 "Software Testing"by Adi.pdf

Software Testing
DR. K. ADISESHA

Software Engineering
Unit-5 Introduction
Software Testing
Development Testing
Test-Driven Development
User Testing
2
Software Testing
Dr. K. Adisesha

Introduction
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Software Testing:
Testing is intended to show that a program does what it is intended to do and to
discover program defects before it is put into use. When you test software, you execute
a program using artificial data.
➢ You check the results of the test run for errors, anomalies or information about the
program's non-functional attributes.
➢ Testing can reveal the presence of errors, but NOT their absence.
➢ Testing is part of a more general verification and validation process, which also
includes static validation techniques.

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Goals of software testing:
To demonstrate to the developer and the customer that the software meets its
requirements.
➢ Leads to validation testing: you expect the system to perform correctly using a given
set of test cases that reflect the system's expected use.
➢ A successful test shows that the system operates as intended.
➢ To discover situations in which the behavior of the software is incorrect, undesirable
or does not conform to its specification.
❖ Leads to defect testing: the test cases are designed to expose defects; the test cases
can be deliberately obscure and need not reflect how the system is normally used.
❖ A successful test is a test that makes the system perform incorrectly and so exposes
a defect in the system.

Introduction
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Testing can be viewed as an input-output process:

Software Testing
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Verification and validation:
Testing is part of a broader process of software verification and validation (V & V).
➢ Verification: Are we building the product right?
❖ The software should conform to its specification.
➢ Validation: Are we building the right product?
❖ The software should do what the user really requires.
➢ The Goal of V & V is to establish confidence that the system is good enough for its intended
use, which depends on:
❖ Software purpose: the level of confidence depends on how critical the software is to an
organization.
❖ User expectations: users may have low expectations of certain kinds of software.
❖ Marketing environment: getting a product to market early may be more important than
finding defects in the program.

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Inspections and testing:
Software inspections involve people examining the source representation with the aim
of discovering anomalies and defects.
➢ Inspections not require execution of a system so may be used before implementation.
➢ They may be applied to any representation of the system (requirements, design,
configuration data, test data, etc.).
➢ They have been shown to be an effective technique for discovering program errors.
➢ Inspections and testing are complementary and not opposing verification techniques.
Both should be used during the V & V process.
➢ Inspections cannot check non-functional characteristics such as performance,
usability, etc.

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➢ Inspections can check conformance with a specification but not conformance with the
customer's real requirements.
➢ Typically, a commercial software system has to go through three stages of testing:
❖ Development testing: the system is tested during development to discover bugs and
defects.
❖ Release testing: a separate testing team test a complete version of the system before it
is released to users.
❖ User testing: users or potential users of a system test the system in their own
environment.

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➢ Advantages of inspections include:
❖ During testing, errors can mask (hide) other errors. Because inspection is a static
process, you don't have to be concerned with interactions between errors.
❖ Incomplete versions of a system can be inspected without additional costs. If a
program is incomplete, then you need to develop specialized test harnesses to test the
parts that are available.
❖ As well as searching for program defects, an inspection can also consider broader
quality attributes of a program, such as compliance with standards, portability and
maintainability.

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Development Testing:
Development testing includes all testing activities that are carried out by the team
developing the system:
➢ Unit testing: individual program units or object classes are tested; should focus on
testing the functionality of objects or methods.
➢ Component testing: several individual units are integrated to create composite
components; should focus on testing component interfaces.
➢ System testing: some or all of the components in a system are integrated and the
system is tested as a whole; should focus on testing component interactions.

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Unit Testing:
Unit testing is the process of testing individual components in isolation. It is a defect
testing process.
➢ Unit testing should be automated so that tests are run and checked without manual
intervention. Units may be:
❖ Individual functions or methods within an object;
❖ Object classes with several attributes and methods;
❖ Composite components with defined interfaces used to access their functionality.
➢ When testing object classes, tests should be designed to provide coverage of all of the
features of the object:
❖ Test all operations associated with the object;
❖ Set and check the value of all attributes associated with the object;
❖ Put the object into all possible states, i.e. simulate all events that cause a state change.

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Unit Testing:
Unit testing frameworks provide generic test classes that you extend to create specific
test cases.
➢ The objective of Unit Testing is:
❖ To isolate a section of code.
❖ To verify the correctness of the code.
❖ To test every function and procedure.
❖ To fix bugs early in the development cycle and to save costs.
❖ To help the developers understand the code base and enable
them to make changes quickly.
❖ To help with code reuse.

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Unit Testing:
Unit testing frameworks provide generic test classes that you extend to create specific
test cases.
➢ In automated unit testing, you make use of a test automation framework (such as JUnit)
to write and run your program tests.
➢ An automated test has three parts:
❖ A setup part, where you initialize the system with the test case, namely the inputs and
expected outputs.
❖ A call part, where you call the object or method to be tested.
❖ An assertion part where you compare the result of the call with the expected result. If
the assertion evaluates to true, the test has been successful if false, then it has failed.

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Unit Testing:
The test cases should show that, when used as expected, the component that you are
testing does what it is supposed to do.
➢ If there are defects in the component, these should be revealed by test cases.
➢ This leads to two types of unit test cases:
❖ The first of these should reflect normal operation of a program and should show that
the component works as expected.
❖ The other kind of test case should be based on testing experience of where common
problems arise. It should use abnormal inputs to check that these are properly
processed and do not crash the component.

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Types of Unit Testing:
There are 2 types of Unit Testing: Manual, and Automated.
➢ There are 3 types of Unit Testing Techniques. They are
❖ Black Box Testing: This testing technique is used in covering the unit tests for input, user
interface, and output parts.
❖ White Box Testing: This technique is used in testing the functional behavior of the system by
giving the input and checking the functionality output including the internal design structure
and code of the modules.
❖ Gray Box Testing: This technique is used in executing the relevant test cases, test methods, and
test functions, and analyzing the code performance for the modules.

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Component Testing:
Software components are often composite components that are made up of several
interacting objects. Testing composite components should therefore focus on showing
that the component interface behaves according to its specification.
➢ Objectives are to detect faults due to interface errors or invalid assumptions about
interfaces.
➢ Interface types include:
❖ Parameter interfaces: data passed from one method or procedure to another.
❖ Shared memory interfaces: block of memory is shared between procedures or functions.
❖ Procedural interfaces: sub-system encapsulates a set of procedures to be called by
other sub-systems.
❖ Message passing interfaces: sub-systems request services from other sub-systems.

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Component Testing:
➢ Interface errors:
❖ Interface misuse: a calling component calls another component and makes an error
in its use of its interface e.g. parameters in the wrong order.
❖ Interface misunderstanding: a calling component embeds assumptions about the
behavior of the called component which are incorrect.
❖ Timing errors: the called and the calling component operate at different speeds and
out-of-date information is accessed.

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Component Testing:
➢ General guidelines for interface testing:
❖ Design tests so that parameters to a called procedure are at the extreme ends of
their ranges.
❖ Always test pointer parameters with null pointers.
❖ Design tests which cause the component to fail.
❖ Use stress testing in message passing systems.
❖ In shared memory systems, vary the order in which components are activated.

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System Testing:
System testing during development involves integrating components to create a version
of the system and then testing the integrated system.
➢ The focus in system testing is testing the interactions between components.
➢ System testing checks that components are compatible, interact correctly and transfer
the right data at the right time across their interfaces.
➢ System testing tests the emergent behavior of a system.
➢ During system testing, reusable components that have been separately developed and
off-the-shelf systems may be integrated with newly developed components.
➢ The complete system is then tested.

Development Testing
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System Testing:
System testing during development involves integrating components to create a version
of the system and then testing the integrated system.
➢ Components developed by different team members or sub-teams may be integrated at
this stage.
➢ System testing is a collective rather than an individual process.
➢ The use cases developed to identify system interactions can be used as a basis for
system testing.
❖ Each use case usually involves several system components so testing the use case forces
these interactions to occur.
❖ The sequence diagrams associated with the use case document the components and
their interactions that are being tested.

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Test-Driven Development:
Test-driven development (TDD) is an approach to program development in which you
inter-leave testing and code development.
➢ Tests are written before code and 'passing' the tests is the critical driver of development.
➢ This is a differentiating feature of TDD versus writing unit tests after the code is
written: it makes the developer focus on the requirements before writing the code.
➢ The code is developed incrementally, along with a test for that increment.
➢ You don't move on to the next increment until the code that you have developed passes
its test.
➢ TDD was introduced as part of agile methods such as Extreme Programming. However,
it can also be used in plan-driven development processes.

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➢ The goal of TDD isn't to ensure we write tests by writing them first, but to produce working
software that achieves a targeted set of requirements using simple, maintainable solutions.
➢ To achieve this goal, TDD provides strategies for keeping code working, simple, relevant, and
free of duplication.

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➢ TDD process includes the following activities:
❖ Start by identifying the increment of functionality that is required. This should normally
be small and implementable in a few lines of code.
❖ Write a test for this functionality and implement this as an automated test.
❖ Run the test, along with all other tests that have been implemented. Initially, you have
not implemented the functionality so the new test will fail.
❖ Implement the functionality and re-run the test.
❖ Once all tests run successfully, you move on to implementing the next chunk of
functionality.

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➢ Benefits of test-driven development:
❖ Code coverage: every code segment that you write has at least one associated test so all
code written has at least one test.
❖ Regression testing: a regression test suite is developed incrementally as a program is
developed.
❖ Simplified debugging: when a test fails, it should be obvious where the problem lies; the
newly written code needs to be checked and modified.
❖ System documentation: the tests themselves are a form of documentation that describe
what the code should be doing.

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➢ Regression testing is testing the system to check that changes have not 'broken'
previously working code.
❖ In a manual testing process, regression testing is expensive but, with automated
testing, it is simple and straightforward.
❖ All tests are rerun every time a change is made to the program. Tests must run
'successfully' before the change is committed.

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➢ Regression testing is testing the system to check that changes have not 'broken'
previously working code.
❖ In a manual testing process, regression testing is expensive but, with automated
testing, it is simple and straightforward.
❖ All tests are rerun every time a change is made to the program. Tests must run
'successfully' before the change is committed.

Release Testing
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Release Testing:
Release testing is the process of testing a particular release of a system that is intended
for use outside of the development team.
➢ The primary goal of the release testing process is to convince the customer of the system
that it is good enough for use.
➢ Release testing, therefore, has to show that the system delivers its specified functionality,
performance and dependability, and that it does not fail during normal use.
➢ Release testing is usually a black-box testing process where tests are only derived from
the system specification.

Release Testing
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Release Testing:
Release testing may involve testing the emergent properties of a system, such as
performance and reliability. Tests should reflect the profile of use of the system.
➢ The objective of release testing is to check that the system meets its requirements and is
good enough for external use (validation testing).
➢ Release testing is a form of system testing. Important differences:
❖ A separate team that has not been involved in the system development, should be
responsible for release testing.
❖ System testing by the development team should focus on discovering bugs in the
system (defect testing).

Release Testing
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Release Testing:
Part of release testing may involve testing the emergent properties of a system, such as
performance and reliability. Tests should reflect the profile of use of the system.
➢ Requirements-based testing involves examining each requirement and developing a test
or tests for it. It is validation rather than defect testing: you are trying to demonstrate
that the system has properly implemented its requirements.
➢ Scenario testing is an approach to release testing where you devise typical scenarios of
use and use these to develop test cases for the system. Scenarios should be realistic and
real system users should be able to relate to them.
➢ Stress testing is a form of performance testing where the system is deliberately
overloaded to test its failure behavior.

User Testing
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User Testing:
User or customer testing is a stage in the testing process in which users or customers
provide input and advice on system testing.
➢ User testing is essential, even when comprehensive system and release testing have been
carried out.
➢ Types of user testing include:
❖ Alpha testing: users of the software work with the development team to test the
software at the developer's site.
❖ Beta testing: a release of the software is made available to users to allow them to
experiment and to raise problems that they discover with the system developers.
❖ Acceptance testing: customers test a system to decide whether or not it is ready to be
accepted from the system developers and deployed in the customer environment.

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User testing:
User or customer testing is a stage in the testing process in which users or customers
provide input and advice on system testing.
➢ In agile methods, the user/customer is part of the development team and is responsible
for making decisions on the acceptability of the system.
➢ Tests are defined by the user/customer and are integrated with other tests in that they
are run automatically when changes are made.
➢ Main problem here is whether or not the embedded user is 'typical' and can represent
the interests of all system stakeholders.

Discussion
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Queries ?
Prof. K. Adisesha
9449081542
Reference: Sommerville, Software Engineering, 10 ed.,

Software Engineering-Unit 5 "Software Testing"by Adi.pdf

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