Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
OBJECT-ORIENTED PROGRAMMING
Visual Basic provides full support
encapsulation, inheritance, and polymorphism.
for
object-oriented
programming
including
Encapsulation means that a group of related properties, methods, and other members are
treated as a single unit or object.
Inheritance describes the ability to create new classes based on an existing class.
Polymorphism means that you can have multiple classes that can be used
interchangeably, even though each class implements the same properties or methods in different
ways.
This section describes the following concepts:
•
Classes and objects
➢ Class members
1) Properties and fields
2) Methods
3) Constructors
4) Destructors
5) Events
6) Nested classes
➢ Access modifiers and access levels
1) Instantiating classes
2) Shared classes and members
3) Anonymous types
➢ Inheritance
1) Overriding members
2) Interfaces
3) Generics
4) Delegates
CLASSES AND OBJECTS
The terms class and object are sometimes used interchangeably, but in fact, classes
describe the type of objects, while objects are usable instances of classes. So, the act of creating
an object is called instantiation. Using the blueprint analogy, a class is a blueprint, and an object
is a building made from that blueprint.
To define a class:
VB
Class SampleClass
End Class
Visual Basic also provides a light version of classes called structures that are useful when
you need to create large array of objects and do not want to consume too much memory for that.
To define a structure:
VB
Structure SampleStructure
End Structure
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
CLASS MEMBERS
Each class can have different class members that include properties that describe class
data, methods that define class behavior, and events that provide communication between
different classes and objects.
To define a field:
VB
Class SampleClass
Public SampleField As String
End Class
Properties have “get” and “set” procedures, which provide more control on how values are set or
returned.
Visual Basic allows you either to create a private field for storing the property value or use
so-called auto-implemented properties that create this field automatically behind the scenes and
provide the basic logic for the property procedures.
To define an auto-implemented property:
VB
Class SampleClass
Public Property SampleProperty as String
End Class
If you need to perform some additional operations for reading and writing the property
value, define a field for storing the property value and provide the basic logic for storing and
retrieving it:
VB
Class SampleClass
Private m_Sample As String
Public Property Sample() As String
Get
' Return the value stored in the field.
Return m_Sample
End Get
Set(ByVal Value As String)
' Store the value in the field.
m_Sample = Value
End Set
End Property
End Class
Most properties have methods or procedures to both set and get the property value.
However, you can create read-only or write-only properties to restrict them from being modified
or read. In Visual Basic you can use ReadOnly and WriteOnly keywords. However, autoimplemented properties cannot be read-only or write-only.
METHODS
A method is an action that an object can perform.
Note:
In Visual Basic, there are two ways to create a method: the Sub statement is used if
the method does not return a value; the Function statement is used if a method returns a
value.
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
To define a method of a class:
VB
Class SampleClass
Public Function SampleFunc(ByVal SampleParam As String)
' Add code here
End Function
End Class
A class can have several implementations, or overloads, of the same method that differ in
the number of parameters or parameter types.
To overload a method:
VB
Overloads Sub Display(ByVal theChar As Char)
' Add code that displays Char data.
End Sub
Overloads Sub Display(ByVal theInteger As Integer)
' Add code that displays Integer data.
End Sub
In most cases you declare a method within a class definition. However, Visual Basic also
supports extension methods that allow you to add methods to an existing class outside the actual
definition of the class.
CONSTRUCTORS
Constructors are class methods that are executed automatically when an object of a given
type is created. Constructors usually initialize the data members of the new object. A constructor
can run only once when a class is created. Furthermore, the code in the constructor always runs
before any other code in a class. However, you can create multiple constructor overloads in the
same way as for any other method.
To define a constructor for a class:
VB
Class SampleClass
Sub New(ByVal s As String)
// Add code here.
End Sub
End Class
DESTRUCTORS
Destructors are used to destruct instances of classes. In the .NET Framework, the
garbage collector automatically manages the allocation and release of memory for the managed
objects in your application. However, you may still need destructors to clean up any unmanaged
resources that your application creates. There can be only one destructor for a class.
EVENTS
Events enable a class or object to notify other classes or objects when something of
interest occurs. The class that sends (or raises) the event is called the publisher and the classes
that receive (or handle) the event are called subscribers. For more information about events, how
they are raised and handled, see Events.
➢ To declare events, use the Event Statement.
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
➢ To raise events, use the RaiseEvent Statement.
➢ To specify event handlers using a declarative way, use the WithEvents statement and the
Handles clause.
➢ To be able to dynamically add, remove, and change the event handler associated with an
event, use the AddHandler Statement and RemoveHandler Statement together with the
AddressOf Operator.
NESTED CLASSES
A class defined within another class is called nested. By default, the nested class is
private.
VB
Class Container
Class Nested
' Add code here.
End Class
End Class
To create an instance of the nested class, use the name of the container class followed by the
dot and then followed by the name of the nested class:
VB
Dim nestedInstance As Container.Nested = New Container.Nested()
ACCESS MODIFIERS AND ACCESS LEVELS
All classes and class members can specify what access level they provide to other classes
by using access modifiers.The following access modifiers are available:
Visual
Basic Modifier
Definition
Public
The type or member can be accessed by any other code in the same assembly or another assembly
that references it.
Private
The type or member can only be accessed by code in the same class.
Protected
The type or member can only be accessed by code in the same class or in a derived class.
Friend
The type or member can be accessed by any code in the same assembly, but not from another
assembly.
Protected
Friend
The type or member can be accessed by any code in the same assembly, or by any derived class in
another assembly.
INSTANTIATING CLASSES
To create an object, you need to instantiate a class, or create a class instance.
VB
Dim sampleObject as New SampleClass()
After instantiating a class, you can assign values to the instance's properties and fields
and invoke class methods.
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
VB
' Set a property value.
sampleObject.SampleProperty = "Sample String"
' Call a method.
sampleObject.SampleMethod()
To assign values to properties during the class instantiation process, use object initializers:
VB
Dim sampleObject = New SampleClass With
{.FirstProperty = "A", .SecondProperty = "B"}
SHARED CLASSES AND MEMBERS
A shared member of the class is a property, procedure, or field that is shared by all
instances of a class.
To define a shared member:
VB
Class SampleClass
Public Shared SampleString As String = "Sample String"
End Class
To access the shared member, use the name of the class without creating an object of this class:
VB
MsgBox(SampleClass.SampleString)
Shared modules in Visual Basic have shared members only and cannot be instantiated.
Shared members also cannot access non-shared properties, fields or methods.
ANONYMOUS TYPES
Anonymous types enable you to create objects without writing a class definition for the
data type. Instead, the compiler generates a class for you. The class has no usable name and
contains the properties you specify in declaring the object.
To create an instance of an anonymous type:
VB
' sampleObject is an instance of a simple anonymous type.
Dim sampleObject =
New With {Key .FirstProperty = "A", .SecondProperty = "B"}
INHERITANCE
Inheritance enables you to create a new class that reuses, extends, and modifies the
behavior that is defined in another class. The class whose members are inherited is called the
base class, and the class that inherits those members is called the derived class. However, all
classes in Visual Basic implicitly inherit from the Object class that supports .NET class hierarchy
and provides low-level services to all classes.
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
Note:
Visual Basic doesn't support multiple inheritance. That is, you can specify only one
base class for a derived class.
To inherit from a base class:
VB
Class DerivedClass
Inherits BaseClass
End Class
By default, all classes can be inherited. However, you can specify whether a class must
not be used as a base class, or create a class that can be used as a base class only.
To specify that a class cannot be used as a base class:
VB
NotInheritable Class SampleClass
End Class
To specify that a class can be used as a base class only and cannot be instantiated:
VB
MustInherit Class BaseClass
End Class
OVERRIDING MEMBERS
By default, a derived class inherits all members from its base class. If you want to change
the behavior of the inherited member, you need to override it. That is, you can define a new
implementation of the method, property or event in the derived class.
The following modifiers are used to control how properties and methods are overridden:
Visual
Basic Modifier
Definition
Overridable
Allows a class member to be overridden in a derived class.
Overrides
Overrides a virtual (overridable) member defined in the base class.
Notoverridable
Prevents a member from being overridden in an inheriting class.
Mustoverride
Requires that a class member to be overridden in the derived class.
Shadows
Hides a member inherited from a base class
INTERFACES
Interfaces, like classes, define a set of properties, methods, and events. But unlike
classes, interfaces do not provide implementation. They are implemented by classes, and defined
as separate entities from classes. An interface represents a contract, in that a class that
implements an interface must implement every aspect of that interface exactly as it is defined.
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
To define an interface:
VB
Public Interface ISampleInterface
Sub DoSomething()
End Interface
To implement an interface in a class:
VB
Class SampleClass
Implements ISampleInterface
Sub DoSomething
' Method implementation.
End Sub
End Class
GENERICS
Classes, structures, interfaces and methods in .NET can include type parameters that
define types of objects that they can store or use. The most common example of generics is a
collection, where you can specify the type of objects to be stored in a collection.
To define a generic class:
VB
Class SampleGeneric(Of T)
Public Field As T
End Class
To create an instance of a generic class:
VB
Dim sampleObject As New SampleGeneric(Of String)
sampleObject.Field = "Sample string"
DELEGATES
A delegate is a type that defines a method signature, and can provide a reference to any
method with a compatible signature. You can invoke (or call) the method through the delegate.
Delegates are used to pass methods as arguments to other methods.
Note:
Event handlers are nothing more than methods that are invoked through delegates.
For more information about using delegates in event handling, see Events.
To create a delegate:
VB
Delegate Sub SampleDelegate(ByVal str As String)
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
To create a reference to a method that matches the signature specified by the delegate:
VB
Class SampleClass
' Method that matches the SampleDelegate signature.
Sub SampleSub(ByVal str As String)
' Add code here.
End Sub
' Method that instantiates the delegate.
Sub SampleDelegateSub()
Dim sd As SampleDelegate = AddressOf SampleSub
sd("Sample string")
End Sub
End Class
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
Software Testing and Quality
WHAT IS QA IN SOFTWARE TESTING?
In the past, quality assurance testing has generally been brought into process relatively
late in the development cycle. For example, in Waterfall, the software is produced and passed
along to the QA team, who offer feedback, then send the software back to development so they
can fix the problems.
Quality Assurance in Software Testing is defined as a procedure to ensure the quality of
software products or services provided to the customers by an organization. Quality assurance
focuses on improving the software development process and making it efficient and effective as
per the quality standards defined for software products. Quality Assurance is popularly known as
QA Testing.
In an Agile environment, everyone, including the Quality Assurance Team, works
collaboratively to make improvements on an ongoing basis. Yet, as developers, operators, and
testers embrace a shared responsibility for making sure they deliver a high-quality end product,
QA often struggles to find its place.
Automated software testing adds another layer of complexity to the mix, which brings up
an important question: what is quality assurance (QA) testing and how does it fit into today’s fastpaced development process?
WHAT IS QUALITY ASSURANCE TESTING?
Quality assurance testing is quality assurance (QA) or a quality testing process that
ensures that an organization delivers the best products or services possible.QA aims to deliver
consistent results through a set of standardized procedures, which means that organizations also
need to make sure that their processes for achieving the desired results hit specific quality
benchmarks themselves.
In brief, you might say that QA includes all activities that center around implementing
standards and procedures associated with ensuring that software meets a certain set of
requirements before it’s released to the public.
The key thing to keep in mind is that QA doesn’t involve the actual testing of products.
Instead, it focuses on the procedures to ensure the best outcome. QA activities are ultimately
process oriented.
HOW TO DO QUALITY ASSURANCE: COMPLETE PROCESS
Quality Assurance methodology has a defined cycle called PDCA cycle or Deming cycle.
The phases of this cycle are:
•
•
•
•
Plan - Organization should plan and establish the process related objectives and
determine the processes that are required to deliver a high-Quality end product.
Do - Development and testing of Processes and also "do" changes in the processes
Check - Monitoring of processes, modify the processes, and check whether it meets the
predetermined objectives
Act - A Quality Assurance tester should implement actions that are necessary to achieve
improvements in the processes
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
Quality Assurance Process
These above steps are repeated to ensure that processes followed in the organization are
evaluated and improved on a periodic basis. Let's look into the above QA Process steps in detail.
An organization must use Quality Assurance to ensure that the product is designed and
implemented with correct procedures. This helps reduce problems and errors, in the final product.
WHAT IS QUALITY CONTROL?
Quality Control, or QC, is a software engineering process, typically used to ensure the
quality of the products or services. It’s a bit different than QA, in that, where quality assurance is
about the process, quality control examines the quality of the end products. QC consists of
product-oriented activities that focus on the final outcome. The objective of quality control is to
ensure the product design meets the requirements and specifications of the customers.
It is a Software Engineering process used to ensure quality in a product or a service. It
does not deal with the processes used to create a product; rather it examines the quality of the
"end products" and the final outcome.
The main aim of Quality control is to check whether the products meet the specifications
and requirements of the customer. If an issue or problem is identified, it needs to be fixed before
delivery to the customer.
QC also evaluates people on their quality level skill sets and imparts training and
certifications. This evaluation is required for the service-based organization and helps provide
"perfect" service to the customers.
If QC should find an issue with the end product, it ideally should be resolved before the
end-customer receives the final product. To put it simply, QC includes everything involved in
making sure that a product or service meets the standard quality requirements and the demands
of customers. It involves testing the effectiveness and outcomes of an actual product, such as
executing software after the software development process to find and fix defects before making
it publicly available. The activities of quality control are product oriented.
WHAT IS TESTING?
Testing refers to the actual testing of a product to meet QC standards. This may involve
using or stress testing the product or seeing if the actual service results match the expected
results. The process identifies problems in the product or service before it goes live.
In software testing, this ensures the identification of errors, bugs, and defects in software.
Testing software involves executing a software component to evaluate its properties. Testing
activities are also product oriented.
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
TESTING, QUALITY ASSURANCE, AND QUALITY CONTROL
Most people get confused when it comes to pin down the differences among Quality Assurance,
Quality Control, and Testing. Although they are interrelated and to some extent, they can be
considered as same activities, but there exist distinguishing points that set them apart. The
following table lists the points that differentiate QA, QC, and Testing.
Quality Assurance
Quality Control
Testing
QA includes activities that ensure the
implementation of processes,
procedures and standards in context to
verification of developed software and
intended requirements.
It includes activities that ensure
the verification of a developed
software with respect to
documented (or not in some
cases) requirements.
It includes activities that
ensure the identification of
bugs/error/defects in a
software.
Focuses on processes and procedures
rather than conducting actual testing on
the system.
Focuses on actual testing by
executing the software with an aim
to identify bug/defect through
implementation of procedures and
process.
Focuses on actual testing.
Process-oriented activities.
Product-oriented activities.
Product-oriented activities.
Preventive activities.
It is a corrective process.
It is a preventive process.
It is a subset of Software Test Life
Cycle (STLC).
QC can be considered as the
subset of Quality Assurance.
Testing is the subset of
Quality Control.
AUDIT AND INSPECTION
Audit − It is a systematic process to determine how the actual testing process is conducted within
an organization or a team. Generally, it is an independent examination of processes involved
during the testing of a software. As per IEEE, it is a review of documented processes that
organizations implement and follow. Types of audit include Legal Compliance Audit, Internal
Audit, and System Audit.
Inspection − It is a formal technique that involves formal or informal technical reviews of any
artifact by identifying any error or gap. As per IEEE94, inspection is a formal evaluation technique
in which software requirements, designs, or codes are examined in detail by a person or a group
other than the author to detect faults, violations of development standards, and other problems.
Formal inspection meetings may include the following processes: Planning, Overview
Preparation, Inspection Meeting, Rework, and Follow-up.
TESTING AND DEBUGGING
Testing − It involves identifying bug/error/defect in a software without correcting it. Normally
professionals with a quality assurance background are involved in bugs identification. Testing is
performed in the testing phase.
Debugging − It involves identifying, isolating, and fixing the problems/bugs. Developers who
code the software conduct debugging upon encountering an error in the code. Debugging is a
part of White Box Testing or Unit Testing. Debugging can be performed in the development phase
while conducting Unit Testing or in phases while fixing the reported bugs.
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
DIFFERENCE BETWEEN QUALITY CONTROL AND QUALITY ASSURANCE?
Sometimes, QC is confused with the QA. Quality control is to examine the product or
service and check for the result. Quality Assurance in Software Engineering is to examine the
processes and make changes to the processes which led to the end-product.
Quality Control Vs Quality Assurance
Examples of QC and QA activities are as follows:
QUALITY CONTROL
ACTIVITIES
WALKTHROUGH
TESTING
INSPECTION
CHECKPOINT REVIEW
QUALITY ASSURANCE ACTIVITIES
Quality Audit
Defining Process
Tool Identification and selection
Training of Quality Standards and Processes
The above activities are concerned with Quality Assurance and Control mechanisms for
any product and not essentially software. With respect to software
•
•
QA becomes SQA (Software Quality Assurance)
QC becomes Software Testing.
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
DIFFERENCES BETWEEN SQA AND SOFTWARE TESTING
Following table explains on differences between SQA and Software Testing:
SQA
Software quality assurance is about engineering
process that ensures quality
SOFTWARE TESTING
Software testing is to test a product for problems before
the product goes live
Involves activities related to the implementation of
processes, procedures, and standards. Example audits training
Involves actives concerning verification of product
example - review testing
Process focused
Preventive technique
Product focused
Corrective technique
Proactive measure
Reactive measure
The scope of SQA applied to all products that will be
created by the organization
The scope of software testing applies to a particular
product being tested.
BEST PRACTICES FOR QUALITY ASSURANCE:
•
•
•
•
•
•
•
Create a Robust Testing Environment
Select release criteria carefully
Apply automated testing to high-risk areas to save money. It helps to fasten the entire
process.
Allocate Time Appropriately for each process
It is important to prioritize bugs fixes based on software usage
Form dedicated security and performance testing team
Simulate customer accounts similar to a production environment
QUALITY ASSURANCE FUNCTIONS:
There are 5 primary Quality Assurance Functions:
1. Technology transfer: This function involves getting a product design document as well
as trial and error data and its evaluation. The documents are distributed, checked and
approved
2. Validation: Here validation master plan for the entire system is prepared. Approval of test
criteria for validating product and process is set. Resource planning for execution of a
validation plan is done.
3. Documentation: This function controls the distribution and archiving of documents. Any
change in a document is made by adopting the proper change control procedure. Approval
of all types of documents.
4. Assuring Quality of products
5. Quality improvement plans
QUALITY ASSURANCE CERTIFICATIONS:
There are several certifications available in the industry to ensure that Organizations follow
Standards Quality Processes. Customers make this as qualifying criteria while selecting a
software vendor.
Tomboc, Angelo G.
BS CoE – 3
Software Design
Research Work #2
May 7, 2021
ISO 9000
This standard was first established in 1987, and it is related to Quality Management
Systems. This helps the organization ensure quality to their customers and other stakeholders.
An organization who wishes to be certified as ISO 9000 is audited based on their functions,
products, services and their processes. The main objective is to review and verify whether the
organization is following the process as expected and check whether existing processes need
improvement.
This certification helps •
•
•
•
Increase the profit of the organization
Improves Domestic and International trade
Reduces waste and increase the productivity of the employees
Provide Excellent customer satisfaction
CMMI LEVEL
The Capability Maturity Model Integrated (CMMI) is a process improvement approach
developed specially for software process improvement. It is based on the process maturity
framework and used as a general aid in business processes in the Software Industry. This model
is highly regarded and widely used in Software Development Organizations.
CMMI has 5 levels. An organization is certified at CMMI level 1 to 5 based on the maturity
of their Quality Assurance Mechanisms.
•
•
•
•
•
Level 1 - Initial: In this stage the quality environment is unstable. Simply, no processes
have been followed or documented
Level 2 - Repeatable: Some processes are followed which are repeatable. This level
ensures processes are followed at the project level.
Level 3 - Defined: Set of processes are defined and documented at the organizational
level. Those defined processes are subject to some degree of improvement.
Level 4 - Managed: This level uses process metrics and effectively controls the processes
that are followed.
Level 5 - Optimizing: This level focuses on the continuous improvements of the processes
through learning & innovation.
CONCLUSION:
Quality Assurance is to check whether the product developed is fit for use. For that,
Organization should have processes and standards to be followed which need to be improved on
a periodic basis. It concentrates mainly on the quality of product/service that we are providing to
the customers during or after implementation of software.