Quality Management PDF

Quality Management 1 Topics covered Software quality  Software standards  Reviews and inspections  Quality management and agile development  Software measurement (in brief)  2 Reviews and inspections 3 Reviews and inspections considerations    A group examines part or all of a p...

Quality Management 1 Topics covered Software quality  Software standards  Reviews and inspections  Quality management and agile development  Software measurement (in brief)  2 Reviews and inspections 3 Reviews and inspections considerations    A group examines part or all of a process or system and its documentation to find potential problems. Software or documents may be 'signed off' at a review which signifies that progress to the next development stage has been approved by management. There are different types of review with different objectives ◦ Inspections for defect removal (product); ◦ Reviews for progress assessment (product and process); ◦ Quality reviews (product and standards). 4 Quality reviews A group of people carefully examine part or all of a software system and its associated documentation.  Code, designs, specifications, test plans, standards, etc. can all be reviewed.  Software or documents may be 'signed off' at a review which signifies that progress to the next development stage has been approved by management.  5 Phases in the review process  Pre-review activities ◦ Pre-review activities are concerned with review planning and review preparation  The review meeting ◦ During the review meeting, an author of the document or program being reviewed should ‘walk through’ the document with the review team.  Post-review activities ◦ These address the problems and issues that have been raised during the review meeting. 6 Distributed reviews    The processes suggested for reviews assume that the review team has a face-to-face meeting to discuss the software or documents that they are reviewing. However, project teams are now often distributed, sometimes across countries or continents, so it is impractical for team members to meet face to face. Remote reviewing can be supported using shared documents where each review team member can annotate the document with their comments. 7 Program inspections These are peer reviews where engineers examine the source of a system with the aim of discovering anomalies and defects.  Inspections do 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.  8 Inspection checklists Checklist of common errors should be used to drive the inspection.  Error checklists are programming language dependent and reflect the characteristic errors that are likely to arise in the language.  In general, the 'weaker' the type checking, the larger the checklist.  Examples: Initialisation, Constant naming, loop termination, array bounds, etc.  9 An inspection checklist (a) Fault class Inspection check Data faults • • • • • Control faults • • • • • Input/out • put faults • • Are all program variables initialized before their values are used? Have all constants been named? Should the upper bound of arrays be equal to the size of the array or Size -1? If character strings are used, is a delimiter explicitly assigned? Is there any possibility of buffer overflow? For each conditional statement, is the condition correct? Is each loop certain to terminate? Are compound statements correctly bracketed? In case statements, are all possible cases accounted for? If a break is required after each case in case statements, has it been included? Are all input variables used? Are all output variables assigned a value before they are output? Can unexpected inputs cause corruption? 10 An inspection checklist (b) Fault class Inspection check Interface faults • • • • Storage faults management • • • Exception management • faults Do all function and method calls have the correct number of parameters? Do formal and actual parameter types match? Are the parameters in the right order? If components access shared memory, do they have the same model of the shared memory structure? If a linked structure is modified, have all links been correctly reassigned? If dynamic storage is used, has space been allocated correctly? Is space explicitly deallocated after it is no longer required? Have all possible error conditions been taken into account? 11 Quality management and agile development 12 Quality management and agile development factors Quality management in agile development 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.  The agile community is fundamentally opposed to what it sees as the bureaucratic overheads of standards-based approaches and quality processes as embodied in ISO 9001.  13 Shared good practice  Check before check-in ◦ Programmers are responsible for organizing their own code reviews with other team members before the code is checked in to the build system.  Never break the build ◦ 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.  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. 14 Reviews and agile methods The review process in agile software development is usually informal.  In Scrum,, there is a review meeting after each iteration of the software has been completed (a sprint review), where quality issues and problems may be discussed.  In Extreme Programming, pair programming ensures that code is constantly being examined and reviewed by another team member.  15 Pair programming This is an approach where 2 people are responsible for code development and work together to achieve this.  Code developed by an individual is therefore constantly being examined and reviewed by another team member.  Pair programming leads to a deep knowledge of a program, as both programmers have to understand the program in detail to continue development.  This depth of knowledge is difficult to achieve in inspection processes and pair programming can find bugs that would not be discovered in formal inspections.  16 Pair programming weaknesses  Mutual misunderstandings ◦ Both members of a pair may make the same mistake in understanding the system requirements. Discussions may reinforce these errors.  Pair reputation ◦ Pairs may be reluctant to look for errors because they do not want to slow down the progress of the project.  Working relationships ◦ The pair’s ability to discover defects is likely to be compromised by their close working relationship that often leads to reluctance to criticize work partners. 17 Agile QM and large systems  When a large system is being developed for an external customer, agile approaches to quality management with minimal documentation may be impractical. ◦ If the customer is a large company, it may have its own quality management processes and may expect the software development company to report on progress in a way that is compatible with them. ◦ Where there are several geographically distributed teams involved in development, perhaps from different companies, then informal communications may be impractical. ◦ For long-lifetime systems, the team involved in development will change. Without documentation, new team members may find it impossible to understand development. 18 Software measurement 19 Software measurement factors Software measurement is concerned with deriving a numeric value for an attribute of a software product or process.  This allows for objective comparisons between techniques and processes.  Although some companies have introduced measurement programmes, most organisations still don’t make systematic use of software measurement.  There are few established standards in this area.  20 Software metric  Any type of measurement which relates to a software system, process or related documentation ◦ Lines of code in a program, the Fog index, number of person-days required to develop a component. Allow the software and the software process to be quantified.  May be used to predict product attributes or to control the software process.  Product metrics can be used for general predictions or to identify anomalous components.  21 Types of process metric  The time taken for a particular process to be completed ◦ This can be the total time devoted to the process, calendar time, the time spent on the process by particular engineers, and so on.  The resources required for a particular process ◦ Resources might include total effort in person-days, travel costs or computer resources.  The number of occurrences of a particular event ◦ Examples of events that might be monitored include the number of defects discovered during code inspection, the number of requirements changes requested, the number of bug reports in a delivered system and the average number of lines of code modified in response to a requirements change. 22 Key points 1   Software quality management is concerned with ensuring that software has a low number of defects and that it reaches the required standards of maintainability, reliability, portability etc. Software standards are important for quality assurance as they represent an identification of ‘best practice’. When developing software, standards provide a solid foundation for building good quality software. Reviews of the software process deliverables involve a team of people who check that quality standards are being followed. Reviews are the most widely used technique for assessing quality. 23 Key points 2    In a program inspection or peer review, a small team systematically checks the code. They read the code in detail and look for possible errors and omissions. The problems detected are discussed at a code review meeting. Agile quality management relies on establishing a quality culture where the development team works together to improve software quality. Software measurement can be used to gather quantitative data about software and the software process. 24 Key points 3 You may be able to use the values of the software metrics that are collected to make inferences about product and process quality.  Product quality metrics are particularly useful for highlighting anomalous components that may have quality problems. These components should then be analyzed in more detail.  Software analytics is the automated analysis of large volumes of software product and process data to discover relationships that may provide insights for project managers and developers.  25