1. Software Testing and Quality Assurance
Lecture 32 – Software Quality Assurance

2. Lecture Objectives A Deeper Understanding of Quality Assurance
Quality Models
Quality Assurance

3. Quality Assurance - Introduction
Quality can not be added to a piece of software after you have built it.
Quality must be built into the software from the beginning.

4. Quality Assurance - Introduction
Two sources of constraints that requires specialized methods:
Non-function requirements that come from the client and their application domain.
Constraints that come from quality standards

5. Quality Assurance for Software Engineers
Quality is a ubiquitous concern in software engineering.
Achieving quality pervades
Software engineering processes, methods, and tools; and
One of the main aims of project managements.

6. Quality Assurance for Software Engineers
Quality products can
Increase market shares,
Long term profitability for companies; and
Poor quality can certainly have the opposite effect.
Yet, in spite of the focus on quality
It can be remarkably elusive to attain in actual software engineering projects.

7. Quality Assurance for Software Engineers
A reason for the concern with quality is the sheer complexity of many modern software systems.
For example,
Approx. 10 Mbytes of object code in an A320 airbus flight control system.
The aircraft has been described as
‘aircraft wrapped around a network’.

8. Quality Assurance for Software Engineers
Complexity in software systems arises in a number of ways.
The large number of modules, concurrent processes, and diversity of platforms that must interact to achieve the aims and requirements of the system; and
The development of the product itself which is subject to changes in requirements, changes in personal and the ever present technological churn.
The phrase mean constantly changing technology
used in implementing and engineering products.

9. What is software Quality?
The End-user’s Perspective
End-users judge the quality of a product by their interaction with it.
For users a system has quality if
It is fit for purpose, reliable and has reasonable performance, easy to learn and use.
Sometime, if the functionality is hard to learn but
is extremely important, then users will still judge the system
to have high quality.

10. What is software Quality?
The Developer’s Perspective
Typically includes the number of faults
Ease of changing the system
Ease of testing the system
The nature of the design
Conformance to requirements;
Resource usage; and performance.

11. What is software Quality?
The Maintainer’s Perspective
Similar to developer’s perspective; but also includes
The simplicity and modularity of the system,
The documentation produced by the developers; and
The ease of understanding the implementation.

12. What is software Quality?
Software engineers need to choose
Processes, tools and techniques to monitor and control the quality of the software as it is being developed.
If we can not directly monitor the attributes,
We often need to monitor the quality of the processes, under the assumption that
The quality of the process influences the quality
of the product.

13. Key points Quality must be built into the software from the beginning.
The evidence suggest that we cannot simply fix up our software post-hoc; and
add in quality attributes after building the system.