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Why does software have bugs?
miscommunication or no communication-as to specifics of what an application should or shouldn't do (the application's requirements).
software complexity-the complexity of current software applications can be difficult to comprehend for anyone without experience in modern-day software development. Windows-type interfaces, client-server and distributed applications, data communications, enormous relational databases, and sheer size of applications have all contributed to the exponential growth in software/system complexity. And the use of object-oriented techniques can complicate instead of simplify a project unless it is well-engineered.
programming errors-programmers, like anyone else, can make mistakes.
changing requirements (whether documented or undocumented) -the customer may not understand the effects of changes, or may understand and request them anyway-redesign, rescheduling of engineers, effects on other projects, work already completed that may have to be redone or thrown out, hardware requirements that may be affected, etc. If there are many minor changes or any major changes, known and unknown dependencies among parts of the project are likely to interact and cause problems, and the complexity of coordinating changes may result in errors. Enthusiasm of engineering staff may be affected. In some fast-changing business environments, continuously modified requirements may be a fact of life. In this case, management must understand the resulting risks, and QA and test engineers must adapt and plan for continuous extensive testing to keep the inevitable bugs from running out of control-see ‘What can be done if requirements are changing continuously?’ in Part 2 of the FAQ.
time pressures-scheduling of software projects is difficult at best, often requiring a lot of guesswork. When deadlines loom and the crunch comes, mistakes will be made.
egos-people prefer to say things like:
- ‘no problem’
- ‘piece of cake’
- ‘I can whip that out in a few hours’
- ‘it should be easy to update that old code’
- instead of:
- ‘that adds a lot of complexity and we could end up making a lot of mistakes’
- ‘we have no idea if we can do that; we'll wing it’
- ‘I can't estimate how long it will take, until I take a close look at it’
- ‘we can't figure out what that old spaghetti code did in the first place’
If there are too many unrealistic ‘no problem's’ the result is bugs.
poorly documented code-it's tough to maintain and modify code that is badly written or poorly documented; the result is bugs. In many organizations management provides no incentive for programmers to document their code or write clear, understandable, maintainable code. In fact, it's usually the opposite: They get points mostly for quickly turning out code, and there's job security if nobody else can understand it ( ‘if it was hard to write, it should be hard to read’ ).
software development tools-visual tools, class libraries, compilers, scripting tools, etc. Often introduce their own bugs or are poorly documented, resulting in added bugs.
How can new Software QA processes be introduced in an existing organization?
A lot depends on the size of the organization and the risks involved. For large organizations with high-risk (in terms of lives or property) projects, serious management buy-in is required and a formalized QA process is necessary.
Where the risk is lower, management and organizational buy-in and QA implementation may be a slower, step-at-a-time process. QA processes should be balanced with productivity so as to keep bureaucracy from getting out of hand.
For small groups or projects, a more ad-hoc process may be appropriate, depending on the type of customers and projects. A lot will depend on team leads or managers, feedback to developers, and ensuring adequate communications among customers, managers, developers, and testers.
The most value for effort will be in requirements management processes, with a goal of clear, complete, testable requirement specifications embodied in requirements or design documentation and design inspections and code inspections.
What is verification? validation?
Verification typically involves reviews and meetings to evaluate documents, plans, code, requirements, and specifications. This can be done with checklists, issues lists, walkthroughs, and inspection meetings. Validation typically involves actual testing and takes place after verifications are completed. The term ‘IV & V’ refers to Independent Verification and Validation.
What is a ‘walkthrough’
A ‘walkthrough’ is an informal meeting for evaluation or informational purposes. Little or no preparation is usually required.
What's an ‘inspection’
An inspection is more formalized than a ‘walkthrough’ typically with 3 − 8 people including a moderator, reader, and a recorder to take notes. The subject of the inspection is typically a document such as a requirements spec or a test plan, and the purpose is to find problems and see what's missing, not to fix anything. Attendees should prepare for this type of meeting by reading thru the document; most problems will be found during this preparation. The result of the inspection meeting should be a written report. Thorough preparation for inspections is difficult, painstaking work, but is one of the most cost effective methods of ensuring quality. Employees who are most skilled at inspections are like the ‘eldest brother’ in the parable in ‘Why is it often hard for management to get serious about quality assurance?’ Their skill may have low visibility but they are extremely valuable to any software development organization, since bug prevention is far more cost-effective than bug detection.
What kinds of testing should be considered?
- Black box testing-not based on any knowledge of internal design or code. Tests are based on requirements and functionality.
- White box testing-based on knowledge of the internal logic of an application's code. Tests are based on coverage of code statements, branches, paths, conditions.
- unit testing-the most ‘micro’ scale of testing; to test particular functions or code modules. Typically done by the programmer and not by testers, as it requires detailed knowledge of the internal program design and code. Not always easily done unless the application has a well-designed architecture with tight code; may require developing test driver modules or test harnesses.
- incremental integration testing-continuous testing of an application as new functionality is added; requires that various aspects of an application's functionality be independent enough to work separately before all parts of the program are completed, or that test drivers be developed as needed; done by programmers or by testers.
- integration testing-testing of combined parts of an application to determine if they function together correctly. The ‘parts’ can be code modules, individual applications, client and server applications on a network, etc. This type of testing is especially relevant to client/server and distributed systems.
- functional testing-black-box type testing geared to functional requirements of an application; this type of testing should be done by testers. This doesn't mean that the programmers shouldn't check that their code works before releasing it (which of course applies to any stage of testing.)
- system testing-black-box type testing that is based on overall requirements specifications; covers all combined parts of a system.
- end-to-end testing-similar to system testing; the ‘macro’ end of the test scale; involves testing of a complete application environment in a situation that mimics real-world use, such as interacting with a database, using network communications, or interacting with other hardware, applications, or systems if appropriate.
- sanity testing or smoke testing-typically an initial testing effort to determine if a new software version is performing well enough to accept it for a major testing effort. For example, if the new software is crashing systems every 5 minutes, bogging down systems to a crawl, or corrupting databases, the software may not be in a ‘sane’ enough condition to warrant further testing in its current state.
- regression testing-re-testing after fixes or modifications of the software or its environment. It can be difficult to determine how much re-testing is needed, especially near the end of the development cycle. Automated testing tools can be especially useful for this type of testing.
- acceptance testing-final testing based on specifications of the end-user or customer, or based on use by end-users/customers over some limited period of time.
- load testing-testing an application under heavy loads, such as testing of a web site under a range of loads to determine at what point the system's response time degrades or fails.
- stress testing-term often used interchangeably with ‘load’ and ‘performance’ testing. Also used to describe such tests as system functional testing while under unusually heavy loads, heavy repetition of certain actions or inputs, input of large numerical values, large complex queries to a database system, etc.
- performance testing-term often used interchangeably with ‘stress’ and ‘load’ testing. Ideally ‘performance’ testing (and any other ‘type’ of testing) is defined in requirements documentation or QA or Test Plans.
- usability testing-testing for ‘user-friendliness’ Clearly this is subjective, and will depend on the targeted end-user or customer. User interviews, surveys, video recording of user sessions, and other techniques can be used. Programmers and testers are usually not appropriate as usability testers.
- install/uninstall testing-testing of full, partial, or upgrade install/uninstall processes.
- recovery testing-testing how well a system recovers from crashes, hardware failures, or other catastrophic problems.
- security testing-testing how well the system protects against unauthorized internal or external access, willful damage, etc; may require sophisticated testing techniques.
- compatability testing-testing how well software performs in a particular hardware/software/operating system/network/etc. Environment.
- exploratory testing-often taken to mean a creative, informal software test that is not based on formal test plans or test cases; testers may be learning the software as they test it.
- ad-hoc testing-similar to exploratory testing, but often taken to mean that the testers have significant understanding of the software before testing it.
- user acceptance testing-determining if software is satisfactory to an end-user or customer.
- comparison testing-comparing software weaknesses and strengths to competing products.
- alpha testing-testing of an application when development is nearing completion; minor design changes may still be made as a result of such testing. Typically done by end-users or others, not by programmers or testers.
- beta testing-testing when development and testing are essentially completed and final bugs and problems need to be found before final release. Typically done by end-users or others, not by programmers or testers.
- mutation testing-a method for determining if a set of test data or test cases is useful, by deliberately introducing various code changes ( ‘bugs’ ) and retesting with the original test data/cases to determine if the ‘bugs’ are detected. Proper implementation requires large computational resources.
What are 5 common problems in the software development process?
- poor requirements-if requirements are unclear, incomplete, too general, or not testable, there will be problems.
- unrealistic schedule-if too much work is crammed in too little time, problems are inevitable.
- inadequate testing-no one will know whether or not the program is any good until the customer complains or systems crash.
- featuritis-requests to pile on new features after development is underway; extremely common.
- miscommunication-if developers don't know what's needed or customer's have erroneous expectations, problems are guaranteed.
What are 5 common solutions to software development problems?
- solid requirements-clear, complete, detailed, cohesive, attainable, testable requirements that are agreed to by all players. Use prototypes to help nail down requirements.
- realistic schedules-allow adequate time for planning, design, testing, bug fixing, re-testing, changes, and documentation; personnel should be able to complete the project without burning out:
- adequate testing-start testing early on, re-test after fixes or changes, plan for adequate time for testing and bug-fixing.
- stick to initial requirements as much as possible-be prepared to defend against changes and additions once development has begun, and be prepared to explain consequences. If changes are necessary, they should be adequately reflected in related schedule changes. If possible, use rapid prototyping during the design phase so that customers can see what to expect. This will provide them a higher comfort level with their requirements decisions and minimize changes later on:
- communication-require walkthroughs and inspections when appropriate; make extensive use of group communication tools-e-mail, groupware, networked bug-tracking tools and change management tools, intranet capabilities, etc. insure that documentation is available and up-to-date-preferably electronic, not paper; promote teamwork and cooperation; use protoypes early on so that customers'expectations are clarified.
What is software ‘quality’
Quality software is reasonably bug-free, delivered on time and within budget, meets requirements and/or expectations, and is maintainable. However, quality is obviously a subjective term. It will depend on who the ‘customer’ is and their overall influence in the scheme of things. A wide-angle view of the ‘customers’ of a software development project might include end-users, customer acceptance testers, customer contract officers, customer management, the development organization's management/accountants/testers/salespeople, future software maintenance engineers, stockholders, magazine columnists, etc. Each type of ‘customer’ will have their own slant on ‘quality’ -the accounting department might define quality in terms of profits while an end-user might define quality as user-friendly and bug-free.
What is ‘good code’
‘Good code’ is code that works, is bug free, and is readable and maintainable. Some organizations have coding ‘standards’ that all developers are supposed to adhere to, but everyone has different ideas about what's best, or what is too many or too few rules. There are also various theories and metrics, such as McCabe Complexity metrics. It should be kept in mind that excessive use of standards and rules can stifle productivity and creativity. ‘Peer reviews’ ‘buddy checks’ code analysis tools, etc. Can be used to check for problems and enforce standards.
For C and C + + coding, here are some typical ideas to consider in setting rules/standards; these may or may not apply to a particular situation:
minimize or eliminate use of global variables.
use descriptive function and method names-use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descriptive (use of more than 20 characters is not out of line); be consistent in naming conventions.
use descriptive variable names-use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descriptive (use of more than 20 characters is not out of line); be consistent in naming conventions.
function and method sizes should be minimized; less than 100 lines of code is good, less than 50 lines is preferable.
function descriptions should be clearly spelled out in comments preceding a function's code.
organize code for readability.
use whitespace generously-vertically and horizontally
each line of code should contain 70 characters max.
one code statement per line.
coding style should be consistent throught a program (eg, use of brackets, indentations, naming conventions, etc.)
in adding comments, err on the side of too many rather than too few comments; a common rule of thumb is that there should be at least as many lines of comments (including header blocks) as lines of code.
no matter how small, an application should include documentaion of the overall program function and flow (even a few paragraphs is better than nothing); or if possible a separate flow chart and detailed program documentation.
make extensive use of error handling procedures and status and error logging.
for C + +, to minimize complexity and increase maintainability, avoid too many levels of inheritance in class heirarchies (relative to the size and complexity of the application). Minimize use of multiple inheritance, and minimize use of operator overloading (note that the Java programming language eliminates multiple inheritance and operator overloading.)
for C + +, keep class methods small, less than 50 lines of code per method is preferable.
for C + +, make liberal use of exception handlers
What is ‘good design’
‘Design’ could refer to many things, but often refers to ‘functional design’ or ‘internal design’ Good internal design is indicated by software code whose overall structure is clear, understandable, easily modifiable, and maintainable; is robust with sufficient error-handling and status logging capability; and works correctly when implemented. Good functional design is indicated by an application whose functionality can be traced back to customer and end-user requirements (See further discussion of functional and internal design in ‘What's the big deal about requirements?’ in FAQ #2.). For programs that have a user interface, it's often a good idea to assume that the end user will have little computer knowledge and may not read a user manual or even the on-line help; some common rules-of-thumb include:
the program should act in a way that least surprises the user
it should always be evident to the user what can be done next and how to exit
the program shouldn't let the users do something stupid without warning them.
What is SEI? CMM? ISO? IEEE? ANSI? Will it help?
SEI = ‘Software Engineering Institute’ at Carnegie-Mellon University; initiated by the U. S. Defense Department to help improve software development processes.
CMM = ‘Capability Maturity Model’ developed by the SEI. It's a model of 5 levels of organizational ‘maturity’ that determine effectiveness in delivering quality software. It is geared to large organizations such as large U. S. Defense Department contractors. However, many of the QA processes involved are appropriate to any organization, and if reasonably applied can be helpful. Organizations can receive CMM ratings by undergoing assessments by qualified auditors.
- Level 1-characterized by chaos, periodic panics, and heroic efforts required by individuals to successfully complete projects. Few if any processes in place; successes may not be repeatable.
- Level 2-software project tracking, requirements management, realistic planning, and configuration management processes are in place; successful practices can be repeated.
- Level 3-standard software development and maintenance processes are integrated throughout an organization; a Software Engineering Process Group is is in place to oversee software processes, and training programs are used to ensure understanding and compliance.
- Level 4-metrics are used to track productivity, processes, and products. Project performance is predictable, and quality is consistently high.
- Level 5-the focus is on continouous process improvement. The impact of new processes and technologies can be predicted and effectively implemented when required.
Perspective on CMM ratings: During 1997 − 2001, 1018 organizations were assessed. Of those, 27% were rated at Level 1, 39% at 2, 23% at 3, 6% at 4, and 5% at 5 (For ratings during the period 1992 − 96, 62% were at Level 1, 23% at 2, 13% at 3, 2% at 4, and 0.4% at 5.). The median size of organizations was 100 software engineering/maintenance personnel; 32% of organizations were USA federal contractors or agencies. For those rated at
Level 1, the most problematical key process area was in Software Quality Assurance.
ISO = ‘International Organisation for Standardization’ -The ISO 9001: 2000 standard (which replaces the previous standard of 1994) concerns quality systems that are assessed by outside auditors, and it applies to many kinds of production and manufacturing organizations, not just software. It covers documentation, design, development, production, testing, installation, servicing, and other processes. The full set of standards consists of: (a) Q9001 − 2000-Quality Management Systems: Requirements (b); Q9000 − 2000-Quality Management Systems: Fundamentals and Vocabulary (c); Q9004 − 2000-Quality Management Systems: Guidelines for Performance Improvements. To be ISO 9001 certified, a third-party auditor assesses an organization, and certification is typically good for about 3 years, after which a complete reassessment is required. Note that ISO certification does not necessarily indicate quality products-it indicates only that documented processes are followed.
- IEEE = ‘Institute of Electrical and Electronics Engineers'-among other things, creates standards such as’ IEEE Standard for Software Test Documentation' (IEEE/ANSI Standard 829), ‘IEEE Standard of Software Unit Testing (IEEE/ANSI Standard 1008),’ IEEE Standard for Software Quality Assurance Plans' (IEEE/ANSI Standard 730), and others.
- ANSI = ‘American National Standards Institute’ the primary industrial standards body in the U. S. publishes some software-related standards in conjunction with the IEEE and ASQ (American Society for Quality).
Other software development process assessment methods besides CMM and ISO 9000 include SPICE, Trillium, TickIT. And Bootstrap.
What is the ‘software life cycle’
The life cycle begins when an application is first conceived and ends when it is no longer in use. It includes aspects such as initial concept, requirements analysis, functional design, internal design, documentation planning, test planning, coding, document preparation, integration, testing, maintenance, updates, retesting, phase-out, and other aspects.
Will automated testing tools make testing easier?
Possibly. For small projects, the time needed to learn and implement them may not be worth it. For larger projects, or on-going long-term projects they can be valuable.
A common type of automated tool is the ‘record/playback’ type. For example, a tester could click through all combinations of menu choices, dialog box choices, buttons, etc. In an application GUI and have them ‘recorded’ and the results logged by a tool. The ‘recording’ is typically in the form of text based on a scripting language that is interpretable by the testing tool. If new buttons are added, or some underlying code in the application is changed, etc. The application might then be retested by just ‘playing back’ the ‘recorded’ actions, and comparing the logging results to check effects of the changes. The problem with such tools is that if there are continual changes to the system being tested, the ‘recordings’ may have to be changed so much that it becomes very time-consuming to continuously update the scripts. Additionally, interpretation and analysis of results (screens, data, logs, etc.) can be a difficult task. Note that there are record/playback tools for text-based interfaces also, and for all types of platforms.
Other automated tools can include:
- code analyzers-monitor code complexity, adherence to standards, etc.
- coverage analyzers-these tools check which parts of the code have been exercised by a test, and may be oriented to code statement coverage, condition coverage, path coverage, etc.
- memory analyzers-such as bounds-checkers and leak detectors.
- load/performance test tools-for testing client/server and web applications under various load
- web test tools-to check that links are valid, HTML code usage is correct, client-side and server-side programs work, a web site's interactions are secure.
- other tools-for test case management, documentation management, bug reporting, and configuration management.