Quality¶
Definition
Quality is a reflection of one or more peoples' assessment of correspondence between their expectations and experience of a product or a service
Can be divided into three categories
- Product Quality
- Process Quality
- Quality of expectations
Cost of bad quality
Direct cost:
- Loss
- Wasted work
- Maintenance usually more expensive than development
Indirect cost
- Follows from poor quality
- Has potentially severe consequences
Quality Management¶
Quality Management consists of
- Quality Assurance
- Plan or design processes to prevent bad quality
- Quality Control
- Monitor that work products meet quality standards
Theory of Cost and Quality¶
- Low quality(low quality management) is initially cheap, but becomes gradually very expensive
- High quality management, has an initial cost when quality processes are defined, but is cheaper later because users are reporting much less errors, and code is more stable
- The amount of quality management should be balanced to the cost – a process that is 100% defect free is often too expensive, so an appropriate compromise is normally made. As a result the initial cost is a little less than for very high quality management, at the cost that slightly more defects are reported over time.
- We plan and design, how and when to do verification and validation in our process
Quality Assurance¶
Validation (fit for use)
- Are we building the right systems?
- Conforms to customers' expectations and experience
Verification (are all requirements implemented)
- Are we building the system right?
- Conforms to specification
- Relatively objective process
Techniques
- Testing of programs and prototypes
- Reviewing of specifications, documentation and programs
In the Different Models¶
Waterfall¶
Incremental¶
Integration and Configuration¶
Quality Management and Agile Development¶
Quality management in agile is informal rather than document-based
It relies on establishing a quality culture, where all team members feel responsible for software quality and take actions to ensure that quality is maintained. This quality culture is established through agile quality practices
Agile Quality Practices¶
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Definition of Done
- Team agree on what criteria must be met before a task is complete
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Sprint Review
- Product Owner and other stakeholders validate the sprint delivery meets expectations
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Check before check-in
- Developers are responsible for organizing their own code reviews with other team members before the code is checked in to the build system
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Never break the build
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Team members should not check in code that causes the system to fail
Developers have to test their code changes against the whole system and be confident that these work as expected
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Fix problems when you see them
- If a programmer discovers problems or obscurities in code developed by someone else, they can fix these directly rather than referring them back to the original developer
Fundamental Process Theory (Process Quality)¶
- A software product can only be as good as the process through which it is produced
- You can only improve the quality of the product if you improve the process
- Repeating the same process, will create same level of quality
- Sources of bad quality can be used as input to improve the process
