Software Quality

Software Quality

• meets requirements
• useful for situations in which the requirements were stated in terms of things that could be measured
• typically be quality inspectors at various points in the assembly line
• requirements are usually written in the form of stories or use cases
• should be traceability between the requirements and the goals of the stakeholder: Vision documents
• Achieving quality: doing things that build a quality product
• Assuring quality: convincing ourselves and others that we are building, or have built a quality product
• Return On Investment

Defects

• Error: A conceptual, syntactic or clerical discrepancy which results in one or more faults in the software
• Fault: A specific manifestation of an error. A discrepancy in the software which can impair its ability to function as intended. An error may be the cause for several faults
• Failure: A software failure occurs when a fault in the computer program is evoked by some input data, resulting in the computer program not correctly computing the required function in an exact manner.
• Defect: Either a fault or discrepancy between code and documentation that results in mischief in the testing, installation, maintenance, or use of software
• errors cause defects, which, in turn, can result in failures
• multiple ways to detect defects
• Reviews are performed by a group of people, including the developer of the code
• An informal review is called a walkthrough.
• A more formal type of review is a formal inspection
• root cause analysis
• Starting with a failure, we ask why did it happen? What was the defect that led to the failure?
• why did the defect occur? What error led to the defect?
• Handling Defects
• Record and categorize the defect
• Identify and record the error
• Look for similar defects and errors
• Categories of Defects
• by nature
• severity
• priority
• Removing Defects
• Change control: When we fix a defect, we are changing the software
• Regression testing: If you make a change to the software, you need to re-run some of the test cases to make sure you haven’t accidentally broken something else.
• Ripple effect: We need to do a careful job of analyzing the changes we make to the software to avoid ripple effects.
• Preventing Defects
• Defect tracking and cataloging
• Continuous Process Improvement

The Quality Triangle

• People, Processes, and Tools
• People
• Software is a labor-intensive operation
• Hire good people.
• Retain good people.
• Train your staff to keep their skills up to date.
• Management:
• Project managers.
• People managers.
• Technical staff:
• Analysts.
• Designers.
• Programmers.
• Quality Assurance Function.
• Testers.
• Configuration Management.
• Software Quality Assurance.
• Processes
• document our processes and standards.
• Based on our own experience
• Based on industry standards
• Maintain
• Train
• Ensure we are following the standards
• This is the role of Software Quality Assurance.
• Tools
• Reduces errors
• Increases productivity and efficiency
• Makes job easier
• Saves money in the long run

Quality Assurance

• People: Quality Organization
• Configuration Management:
• responsible for version control of the artifacts being produced by the developers
• code, of course, but also requirements and design documentation
• Testing
• developers themselves are responsible for unit testing of their own pieces of work
• separate group of people responsible for larger scale testing
• Software Quality Assurance.
• managerially Independent from the developers, as well as configuration management and testing
• ensures that standards are in place and are approved
• ensure that the standards are placed under configuration control
• runs periodic reviews to ensure that the standards are being followed
• assures all stakeholders of the quality of the workmanship of the rest of the team
• Process: Standards
• Standards are embodiments of best practices
• Government standards
• IEEE standards
• ISO standards
• Tools
• Computer-Aided Software Engineering
• Upper CASE tools
• Planning and estimating.
• Project management.
• Requirements analysis.
• Analysis and design.
• Lower CASE tools
• Coding and reuse.
• Analyzing code.
• Testing.
• Configuration management.
• Metrics.
• Documentation.
• Maintenance.