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What is 'Software Quality Assurance'?
Software QA involves the entire software development PROCESS -
monitoring and improving the process, making sure that any agreed-upon
standards and procedures are followed, and ensuring that problems are
found and dealt with. It is oriented to 'prevention'.
(See the Bookstore for useful books on Software
Quality Assurance.)
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What is 'Software Testing'?
Testing involves operation of a system or application under controlled
conditions and evaluating the results (e.g., 'if the user is in
interface A of the application while using hardware B, and does C, then
D should happen'). The controlled conditions should include both normal
and abnormal conditions. Testing should intentionally attempt to make
things go wrong to determine if things happen when they shouldn't or
things don't happen when they should. It is oriented to 'detection'.
(See the Bookstore for
useful books on Software Testing.)
- Organizations vary considerably in how they assign
responsibility for QA and testing. Sometimes they're the combined
responsibility of one group or individual. Also common are project
teams that include a mix of testers and developers who work closely
together, with overall QA processes monitored by project managers.
It will depend on what best fits an organization's size and business
structure.
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What are some recent major computer system failures
caused by software bugs?
- A September 2006 news report indicated problems with software
utilized in a state government's primary election, resulting in
periodic unexpected rebooting of voter check in machines, which were
separate from the electronic voting machines, and resulted in
confusion and delays at voting sites. The problem was reportedly due
to insufficient testing.
- In August of 2006 a U.S. government student loan service
erroneously made public the personal data of as many as 21,000
borrowers on it's web site, due to a software error. The bug was
fixed and the government department subsequently offered to arrange
for free credit monitoring services for those affected.
- A software error reportedly resulted in over billing of up to
several thousand dollars to each of 11,000 customers of a major
telecommunications company in June of 2006. It was reported that the
software bug was fixed within days, but that correcting the billing
errors would take much longer.
- News reports in May of 2006 described a multi-million dollar
lawsuit settlement paid by a healthcare software vendor to one of
its customers. It was reported that the customer claimed there were
problems with the software they had contracted for, including poor
integration of software modules, and problems that resulted in
missing or incorrect data used by medical personnel.
- In early 2006 problems in a government's financial monitoring
software resulted in incorrect election candidate financial reports
being made available to the public. The government's election
finance reporting web site had to be shut down until the software
was repaired.
- Trading on a major Asian stock exchange was brought to a halt in
November of 2005, reportedly due to an error in a system software
upgrade. The problem was rectified and trading resumed later the
same day.
- A May 2005 newspaper article reported that a major hybrid car
manufacturer had to install a software fix on 20,000 vehicles due to
problems with invalid engine warning lights and occasional stalling.
In the article, an automotive software specialist indicated that the
automobile industry spends $2 billion to $3 billion per year fixing
software problems.
- Media reports in January of 2005 detailed severe problems with a
$170 million high-profile U.S. government IT systems project.
Software testing was one of the five major problem areas according
to a report of the commission reviewing the project. In March of
2005 it was decided to scrap the entire project.
- In July 2004 newspapers reported that a new government welfare
management system in Canada costing several hundred million dollars
was unable to handle a simple benefits rate increase after being put
into live operation. Reportedly the original contract allowed for
only 6 weeks of acceptance testing and the system was never tested
for its ability to handle a rate increase.
- Millions of bank accounts were impacted by errors due to
installation of inadequately tested software code in the transaction
processing system of a major North American bank, according to
mid-2004 news reports. Articles about the incident stated that it
took two weeks to fix all the resulting errors, that additional
problems resulted when the incident drew a large number of e-mail
phishing attacks against the bank's customers, and that the total
cost of the incident could exceed $100 million.
- A bug in site management software utilized by companies with a
significant percentage of worldwide web traffic was reported in May
of 2004. The bug resulted in performance problems for many of the
sites simultaneously and required disabling of the software until
the bug was fixed.
- According to news reports in April of 2004, a software bug was
determined to be a major contributor to the 2003 Northeast blackout,
the worst power system failure in North American history. The
failure involved loss of electrical power to 50 million customers,
forced shutdown of 100 power plants, and economic losses estimated
at $6 billion. The bug was reportedly in one utility company's
vendor-supplied power monitoring and management system, which was
unable to correctly handle and report on an unusual confluence of
initially localized events. The error was found and corrected after
examining millions of lines of code.
- In early 2004, news reports revealed the intentional use of a
software bug as a counter-espionage tool. According to the report,
in the early 1980's one nation surreptitiously allowed a hostile
nation's espionage service to steal a version of sophisticated
industrial software that had intentionally-added flaws. This
eventually resulted in major industrial disruption in the country
that used the stolen flawed software.
- A major U.S. retailer was reportedly hit with a large government
fine in October of 2003 due to web site errors that enabled
customers to view one another's' online orders.
- News stories in the fall of 2003 stated that a manufacturing
company recalled all their transportation products in order to fix a
software problem causing instability in certain circumstances. The
company found and reported the bug itself and initiated the recall
procedure in which a software upgrade fixed the problems.
- In August of 2003 a U.S. court ruled that a lawsuit against a
large online brokerage company could proceed; the lawsuit reportedly
involved claims that the company was not fixing system problems that
sometimes resulted in failed stock trades, based on the experiences
of 4 plaintiffs during an 8-month period. A previous lower court's
ruling that "...six miscues out of more than 400 trades does not
indicate negligence." was invalidated.
- In April of 2003 it was announced that a large student loan
company in the U.S. made a software error in calculating the monthly
payments on 800,000 loans. Although borrowers were to be notified of
an increase in their required payments, the company will still
reportedly lose $8 million in interest. The error was uncovered when
borrowers began reporting inconsistencies in their bills.
- News reports in February of 2003 revealed that the U.S. Treasury
Department mailed 50,000 Social Security checks without any
beneficiary names. A spokesperson indicated that the missing names
were due to an error in a software change. Replacement checks were
subsequently mailed out with the problem corrected, and recipients
were then able to cash their Social Security checks.
- In March of 2002 it was reported that software bugs in Britain's
national tax system resulted in more than 100,000 erroneous tax
overcharges. The problem was partly attributed to the difficulty of
testing the integration of multiple systems.
- A newspaper columnist reported in July 2001 that a serious flaw
was found in off-the-shelf software that had long been used in
systems for tracking certain U.S. nuclear materials. The same
software had been recently donated to another country to be used in
tracking their own nuclear materials, and it was not until
scientists in that country discovered the problem, and shared the
information, that U.S. officials became aware of the problems.
- According to newspaper stories in mid-2001, a major systems
development contractor was fired and sued over problems with a large
retirement plan management system. According to the reports, the
client claimed that system deliveries were late, the software had
excessive defects, and it caused other systems to crash.
- In January of 2001 newspapers reported that a major European
railroad was hit by the aftereffects of the Y2K bug. The company
found that many of their newer trains would not run due to their
inability to recognize the date '31/12/2000'; the trains were
started by altering the control system's date settings.
- News reports in September of 2000 told of a software vendor
settling a lawsuit with a large mortgage lender; the vendor had
reportedly delivered an online mortgage processing system that did
not meet specifications, was delivered late, and didn't work.
- In early 2000, major problems were reported with a new computer
system in a large suburban U.S. public school district with 100,000+
students; problems included 10,000 erroneous report cards and
students left stranded by failed class registration systems; the
district's CIO was fired. The school district decided to reinstate
it's original 25-year old system for at least a year until the bugs
were worked out of the new system by the software vendors.
- A review board concluded that the NASA Mars Polar Lander failed
in December 1999 due to software problems that caused improper
functioning of retro rockets utilized by the Lander as it entered
the Martian atmosphere.
- In October of 1999 the $125 million NASA Mars Climate Orbiter
spacecraft was believed to be lost in space due to a simple data
conversion error. It was determined that spacecraft software used
certain data in English units that should have been in metric units.
Among other tasks, the orbiter was to serve as a communications
relay for the Mars Polar Lander mission, which failed for unknown
reasons in December 1999. Several investigating panels were convened
to determine the process failures that allowed the error to go
undetected.
- Bugs in software supporting a large commercial high-speed data
network affected 70,000 business customers over a period of 8 days
in August of 1999. Among those affected was the electronic trading
system of the largest U.S. futures exchange, which was shut down for
most of a week as a result of the outages.
- In April of 1999 a software bug caused the failure of a $1.2
billion U.S. military satellite launch, the costliest unmanned
accident in the history of Cape Canaveral launches. The failure was
the latest in a string of launch failures, triggering a complete
military and industry review of U.S. space launch programs,
including software integration and testing processes. Congressional
oversight hearings were requested.
- A small town in Illinois in the U.S. received an unusually large
monthly electric bill of $7 million in March of 1999. This was about
700 times larger than its normal bill. It turned out to be due to
bugs in new software that had been purchased by the local power
company to deal with Y2K software issues.
- In early 1999 a major computer game company recalled all copies
of a popular new product due to software problems. The company made
a public apology for releasing a product before it was ready.
- The computer system of a major online U.S. stock trading service
failed during trading hours several times over a period of days in
February of 1999 according to nationwide news reports. The problem
was reportedly due to bugs in a software upgrade intended to speed
online trade confirmations.
- In April of 1998 a major U.S. data communications network failed
for 24 hours, crippling a large part of some U.S. credit card
transaction authorization systems as well as other large U.S. bank,
retail, and government data systems. The cause was eventually traced
to a software bug.
- January 1998 news reports told of software problems at a major
U.S. telecommunications company that resulted in no charges for long
distance calls for a month for 400,000 customers. The problem went
undetected until customers called up with questions about their
bills.
- In November of 1997 the stock of a major health industry company
dropped 60% due to reports of failures in computer billing systems,
problems with a large database conversion, and inadequate software
testing. It was reported that more than $100,000,000 in receivables
had to be written off and that multi-million dollar fines were
levied on the company by government agencies.
- A retail store chain filed suit in August of 1997 against a
transaction processing system vendor (not a credit card company) due
to the software's inability to handle credit cards with year 2000
expiration dates.
- In August of 1997 one of the leading consumer credit reporting
companies reportedly shut down their new public web site after less
than two days of operation due to software problems. The new site
allowed web site visitors instant access, for a small fee, to their
personal credit reports. However, a number of initial users ended up
viewing each others' reports instead of their own, resulting in
irate customers and nationwide publicity. The problem was attributed
to "...unexpectedly high demand from consumers and faulty software
that routed the files to the wrong computers."
- In November of 1996, newspapers reported that software bugs
caused the 411 telephone information system of one of the U.S.
RBOC's to fail for most of a day. Most of the 2000 operators had to
search through phone books instead of using their 13,000,000-listing
database. The bugs were introduced by new software modifications and
the problem software had been installed on both the production and
backup systems. A spokesman for the software vendor reportedly
stated that 'It had nothing to do with the integrity of the
software. It was human error.'
- On June 4 1996 the first flight of the European Space Agency's
new Ariane 5 rocket failed shortly after launching, resulting in an
estimated uninsured loss of a half billion dollars. It was
reportedly due to the lack of exception handling of a floating-point
error in a conversion from a 64-bit integer to a 16-bit signed
integer.
- Software bugs caused the bank accounts of 823 customers of a
major U.S. bank to be credited with $924,844,208.32 each in May of
1996, according to newspaper reports. The American Bankers
Association claimed it was the largest such error in banking
history. A bank spokesman said the programming errors were corrected
and all funds were recovered.
- Software bugs in a Soviet early-warning monitoring system nearly
brought on nuclear war in 1983, according to news reports in early
1999. The software was supposed to filter out false missile
detections caused by Soviet satellites picking up sunlight
reflections off cloud-tops, but failed to do so. Disaster was
averted when a Soviet commander, based on what he said was a
'...funny feeling in my gut', decided the apparent missile attack
was a false alarm. The filtering software code was rewritten.
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Does every software project need testers?
While all projects will benefit from testing, some projects may not
require independent test staff to succeed.
Which projects may not need independent test staff? The answer
depends on the size and context of the project, the risks, the
development methodology, the skill and experience of the developers, and
other factors. For instance, if the project is a short-term, small, low
risk project, with highly experienced programmers utilizing thorough
unit testing or test-first development, then test engineers may not be
required for the project to succeed.
In some cases an IT organization may be too small or new to have a
testing staff even if the situation calls for it. In these circumstances
it may be appropriate to instead use contractors or outsourcing, or
adjust the project management and development approach (by switching to
more senior developers and agile test-first development, for example).
Inexperienced managers sometimes gamble on the success of a project by
skipping thorough testing or having programmers do post-development
functional testing of their own work, a decidedly high risk gamble.
For non-trivial-size projects or projects with non-trivial risks, a
testing staff is usually necessary. As in any business, the use of
personnel with specialized skills enhances an organization's ability to
be successful in large, complex, or difficult tasks. It allows for both
a) deeper and stronger skills and b) the contribution of differing
perspectives. For example, programmers typically have the perspective of
'what are the technical issues in making this functionality work?'. A
test engineer typically has the perspective of 'what might go wrong with
this functionality, and how can we ensure it meets expectations?'.
Technical people who can be highly effective in approaching tasks from
both of those perspectives are rare, which is why, sooner or later,
organizations bring in test specialists.
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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. Multi-tiered
applications, 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.
- programming errors - programmers, like anyone else, can make
mistakes.
- changing requirements (whether documented or undocumented) - the
end-user 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.
- 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.
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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 often be in (a) requirements
management processes, with a goal of clear, complete, testable
requirement specifications embodied in requirements or design
documentation, or in 'agile'-type environments extensive continuous
coordination with end-users, (b) design inspections and code
inspections, and (c) post-mortems/retrospectives.
- Other possibilities include incremental self-managed team
approaches such as 'Kaizen' methods of continuous process
improvement, the Deming-Shewhart Plan-Do-Check-Act cycle, and
others.
(See the Bookstore for
useful books with more information.)
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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.
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What is a 'walkthrough'?
A 'walkthrough' is an informal meeting for evaluation or informational
purposes. Little or no preparation is usually required.
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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 organizations 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.
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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.
- failover testing - typically used interchangeably with 'recovery
testing'
- security testing - testing how well the system protects against
unauthorized internal or external access, willful damage, etc; may
require sophisticated testing techniques.
- compatibility 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.
- context-driven testing - testing driven by an understanding of
the environment, culture, and intended use of software. For example,
the testing approach for life-critical medical equipment software
would be completely different than that for a low-cost computer
game.
- 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.
(See the Bookstore for
useful books on Software
Testing.)
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What are 5 common problems in the software development process?
- poor requirements - if requirements are unclear, incomplete, too
general, and 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.
(See the Bookstore for useful books with more information.)
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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. In 'agile'-type
environments, continuous close coordination with customers/end-users
is necessary.
- 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.
'Early' testing ideally includes unit testing by developers and
built-in testing and diagnostic capabilities.
- stick to initial requirements as much as possible - be prepared
to defend against excessive 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, work closely with customers/end-users to
manage expectations. This will provide them a higher comfort level
with their requirements decisions and minimize excessive changes
later on.
- communication - require walkthroughs and inspections when
appropriate; make extensive use of group communication tools -
groupware, wiki's, bug-tracking tools and change management tools,
intranet capabilities, etc.; insure that information/documentation
is available and up-to-date - preferably electronic, not paper;
promote teamwork and cooperation; use prototypes and/or continuous
communication with end-users if possible to clarify expectations.
(See the Bookstore for useful books with more information.)
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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. (See the
Bookstore
section's 'Software QA' category for useful books with more
information.)
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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 white space generously - vertically and horizontally
- each line of code should contain 70 characters max.
- one code statement per line.
- coding style should be consistent throughout a program (e.g., 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 documentation
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 hierarchies (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
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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.
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.
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What is SEI? CMM? CMMI? 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', now called the CMMI
('Capability Maturity Model Integration'), developed by the SEI.
It's a model of 5 levels of process '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 CMMI 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 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 continuous 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
U.S. federal contractors or agencies. For those rated at
Level 1, the most problematical key process area was in
Software Quality Assurance.
- ISO = 'International Organization 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. Also see
http://www.iso.org/ for the latest
information.
ISO 9126 defines six high level quality characteristics that can be
used in software evaluation. It includes functionality, reliability,
usability, efficiency, maintainability, and portability.
- 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/IT management process assessment
methods besides CMMI and ISO 9000 include SPICE, Trillium, TickIT,
Bootstrap, ITIL, MOF, and CobiT.
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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. (See the
Bookstore
section's 'Software QA', 'Software Engineering', and 'Project
Management' categories for useful books with more information.)
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Courtesy of
www.softwareqatest.com
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