Bab 1 Fundamentals Of Testing

Fundamentals Of
Testing
Lola Yoriva
Program Studi S1 Sistem Informasi
Fakultas Sains dan Teknologi
Universitas Islam Negeri Sultan Syarif Kasim Riau

Fundamentals Of Testing
• Why is testing necessary?
• What is testing?
• Testing Principles
• Fundamental Test Process
• How much testing is enough?
• Why Testers?

Why is testing necessary
• Software system context
• Couses of software defects
• Why we test?
• Cost of software quality

Why is testing necessary?
• Software system context
- Software can be found in many areas of life
- When a system go wrong, it can result many effects start from user inconvenience,
including loss of money, time or business reputation, and could even cause loss a life

• Health equipment
• TransportationsMission Critical
• Banking
• InsuranceBusiness
• Education
• Scientific ResearchOthers

Errors &
Mistakes
- Documents
- Code
- Software System
Failure
Defect or Fault

• Causes of Software Defects
 Humans do mistakes
 Mistakes my lead do defects in source code or system specifications
 Defects are detected only when they leads to failures (code is executed), not all defects
do so
 Failures are considered problems when they occurred in live systems
 An observed failure is an incident

Defect
Injection
Detection
Prevention
- A defect injected at the
time the causing error is
made
- A defect is detected at
the time when failure
occurs
- Finding defects in
requirements docs or static
code can prevent detecting
them in running systems

• Why we Test ( Testing Goals )
Find defects
Measure quality
Provide confidence

• Costs of software defects
 Msnbc published the news of 2000 bug hits millions of German bank cards
 Guardian.co.uk said they paid about (€300m)
 Apple Maps gives us directions to now here (2012)

Risks (Poor
Quality)
Economy
(Money, Time)
Humans
(Death, Injury)
Business
(Reveneu,
Reputation)

Fundamentals of Testing

What is testing?
• The process consisting of all life cycle activities, both static and dynamic
concerned with planning, preparation and evaluation of software products
and related work products to determine that they satisfy specified
requirements, to demonstrate that they are fit for purpose and to detect
defects.

What is Testing?
• Executing SW is only part of testing, other activities exist before and afer
execution
• Testing activities include: planning and control, choosing test conditions,
designing test cases and checking results, evaluating exit criteria, reporting
and closure

Testing Principles
• Testing Shows Presence of defects
• Exhaustive testing is impossible
• Early Testing
• Defect Clustering
• Presticide Paradox
• Testing is context dependent
• Absence of errors fallacy

Testing Principles
• Testing Shows the presence of defects
 Testing can show that defects are presents, but cannot prove that there are no defects
 Testing reduces the probability of undiscovered defects remaining in the software
 Discovering no more defects is not a proof of correctness

Testing principles
• Exhaustive testing is impossible
Testing everything (all combinations of inputs and perconditions) is not feasible except
for trivial cases
Instead of exhaustive testing, risk analysis and priorities should be used to focus testing
efforts
Example: a simple screen with five input fields and to distinct values for each field has
10^5 different combination

Testing Principles
• Early Testing
o The earlier defects are detected, the lower the cost of correction
o To find defects early, testing activities shall be started as early as possible in the software
or system development life cycle, and shall be focused on defined objectives

Testing Principles
• Defects Clustering
 System modules vary in size, complexity and frequency of change
 System modules do not experience the sama defect density or failure rate
 Thus, pareto principle (80-20 rule) is applicable:
A small number of modules contains most of the defects discovered
during prerelease testing, or show the most optional failures

Testing Principles
• Defect Clustering Cont’d
 When a defect is found in one area, changes are there that more defects can be found
and more time can be invested there
 Testers should not ignore any area as defects can be scattered around

Testing Principles
• Pesticide Paradox
- If the same tests are repeated over and over again, eventually the same set of tests cases
will no longer find any new defects
- To overcome this, tests cases need to be regularly reviewed and revised
- New and different tests need to be written to exercise different part of the software or
system to find potentially more defects

Testing Principles
• Testing is context dependent
 Testing is done differently in different contexts
 Fo example, safety-critical software is tested differently from an e-commerce site

Testing Principles
• Absence of Error Fallacy
Finding and fixing defects does not help if the system built is unusable and does not
fulfill the users needs and ecpectations

Planning
and
Control
Implementat
ion and
execution
Analysis
and
design
Closure
Evaluating
exit criteria
and
reporting

Fundamental Test Process
• Planning and Control
 Ongoing comparison of actual progress against plan
 Reporting
 Takes into account feedback of monitoring and control

• Analysis and design
 Reviewing the test basis
 Evaluating testability of test basis and test objects
 Identifying and prioritizing test conditions
 Designing and prioritizing test cases
 Identifying necessary test data
 Designing the test environment set-up and identifying any required infrastructure and
tools

• Implementation and execution
o Creating test cases, writing test procedures
o Creating test suits
o Prepare test execution plans

• Evaluating Exit Criteria and Reporting
 Checking test logs against the exit criteria specified in the planning
 Assessing if more tests are needed
 Writing a test summary report for stake holders

• Test Closure
o Checking that deliverables have been delivered as planned
o Archiving the test environment and the test infrastructure for later reuse
o Analyzing lessons learned for future releases and projects

How much testing is enough?
• The amount of testing needed is proportionate with:
 Risk
 Defect cost
 Information needed
 Project constraints
 Test infrastructure

• Why Testers?

Why Testers?
• Characteristic of a tester
 Curiosity
 Clear thinking skills
 Top flight reading speed and comprehension
 Attention to details
 Quick learner (outside of testing)

Reference
Graham, d., et al. 2006. foundations of software testing: ISTQB certification
London, UK: international Thomson business press.
http://www.uin-suska.ac.id/ http://sif.uin-suska.ac.id/ http://fst.uin-suska.ac.id/

Bab 1 Fundamentals Of Testing

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