3. What is test?
• Testing is the process of exercising or
evaluating a system or system component
by manual or automated means to verify
that it satisfies specified requirements
4. Some English…
• Verification : Methods to ensure that the
system complies with an organizational
standard or process
• Validation: Ensure that the system operates
according to a plan by executing system
functions
5. Why is testing necessary?
• Because software is likely to have faults
• To learn about the reliability of the
software
• Because failures can be very expensive
• To avoid being sued by customers
• To stay in business
6. What is bug?
• A fault in a program which causes the
program to perform in an unintended or
unanticipated manner.
7. Failure
• Deviation of the software from its expected
delivery or service
• Failure is an event
8. Fault
• Cause that failure is caused
• Defect or error inside a program
It is said to be a bug generally
9. Error
• A human action that produces an incorrect
result
Mistake
Oversight
Hand omission
10. Relation of failure, fault and error
A person
makes
an error ...
… that creates
a
fault in the
software ...
… that can
cause
a failure
in operation
11. “Importance” of bugs (in $$)
• Frequency (Fre)
• Correction cost (Cor):
– Typically, significantly more the later the bug is
discovered
• Installation cost (Ins):
– Cost of installing the fix
• Consequences (Con)
12. “Importance” of bugs (Con.)
• Importance = Fre * (Cor + Ins + Con)
– It’s not obvious that these costs can simply be
added.
– Another cost item may be “bug maintenance”: help
desk effort, etc., to assist users to work around it
15. Not all bugs are equal
Fatal
Damage
Serious
Medium
Cosmetic
Bug Type
16. Bug severity
• Cosmetic bugs
– A defect that in no way affects the performance of
the product. It may be a grammatical error
• Medium bugs
– This defect doesn’t stop the user from proceeding,
but causes inconvenience
17. Bug severity (Con.)
• Serious bugs
– System cannot work around
• Fatal bugs
– Defects may stop the user from using the system
further, the system is crashed
18. Bug Status
• ERROR
– The defect is not fixed, or fixed but not satisfactorily
as required
• ASSIGNED
– The defect is reviewed and assigned to fix it
• PENDING
– The defect is already fixed and waiting to retest
19. Bug Status (Con.)
• TESTED
– The defect is fixed satisfactorily as required
• ACCEPTED
– The defect has not been fixed satisfactorily as
required, but it’s accepted by concession of authority
or customer
• CANCELLED
– It’s not a defect or defect is removed by actions
other than bug fixing
21. Bug classification (Con.)
• Requirements & Feature Bugs
– Requirements bugs are the first to invade the system
and the last to leave
– Specs are often self-contradictory, incomplete and
ambiguous
– Extra features, other gratuitous enhancements tend
to be error prone
– Feature interaction problems
22. Bug classification (Con.)
• Structural Bugs
–
–
–
–
Control and sequence bugs
Logic bugs
Processing bugs
Initialization and dataflow bugs
26. Bug classification (Con.)
• Initialization and data bugs
–
–
–
–
–
Improper initialization
Using an un-initialized variable
Double initialization
Modifying data but not keeping the result
Dangling pointers
27. Bug classification (Con.)
• Coding Bugs
–
–
–
Typos
Misunderstood language syntax and semantics
Erroneous comments
28. Bug classification (Con.)
• Interface, Integration & System Bugs
–
–
–
External interfaces
Internal interfaces
Bugs related to hardware, system software, or OS
interface
– Integration bugs
29. Bug classification (Con.)
• Tests & Test Design Bugs
–
–
Bugs in the test (“scaffolding”) software
Bugs in test data
30. Bug Tracking Tools
• Trakium: Issue Tracking System
–
–
Vendor: Multitech
www.trakium.com
• Test Director: Provide -Requirements
Management, Test Plan, Test Case, and Defects
Management
–
–
Vendor: Mercury
www.mercury.com
Process:
Sequence of steps performed for a given purpose. (IEEE – Institute Electrical & Electronic Engineers )
Software Process
A set of activities, methods, practices, and transformations that people use to develop and maintain software and associated products.(SEI-CMM – Software Engineering Institute – Capability Maturity Model for Software)
if executed, a fault may cause a failure
also known as a defect or bug
fault is a state of the software, caused by an error
