Taxonomy for bugs

Taxonomy for Bugs
Harika
Assistant Professor

Taxonomy for Bugs
 Bugs:---
 Requirements, features and functionality
Bugs
 Structural Bugs
 Data Bugs
 Coding Bugs
 Interface, integration and system Bugs
 Test and Test Design Bugs

Requirements, Features,
Functionality Bugs
 3 types of bugs :
 Requirement & Specifications,Requirement & Specifications,
 Feature bugs, &Feature bugs, &
 feature interaction bugsfeature interaction bugs

1. Requirements & Specification Bugs.
– Incompleteness, ambiguous or self-contradictory.
– Analyst’s assumptions not known to the designer.
– Some thing may miss when specs change.
– These are expensive: introduced early in SDLC and
removed at the last.
2.Feature Bugs
– Specification problems create feature bugs
– Wrong feature bug has design implications
– Missing feature is easy to detect & correct
– Unnecessary enhancements can accumulate
bugs, if they increase complexity
– When the features are eliminated, the following
consequences arise
– s/w becomes sophisticated
– Consume more resources
– Additional bugs are stimulated

III. Feature Interaction Bugs
– Arise due to unpredictable interactions between feature groups or
individual features.
– The earlier removed the better as these are costly if detected at the
end.
– Examples: call forwarding & call waiting.
Remedies:
Use high level formal specification languages to eliminate
human-to-human communication
It’s only a short term support & not a long term solution.
Short-term Support:
Specification languages formalize requirements & so
automatic test generation is possible. It’s cost-effective.
Long-term support:
Even with a great specification language, problem is not
eliminated, but is shifted to a higher level. Simple
ambiguities & contradictions may only be removed,
leaving tougher bugs.

Testing Techniques for functional bugs:
Functional test techniques - transactiontransaction
flow testing, syntax testing, domainflow testing, syntax testing, domain
testing, logic testing, and state testingtesting, logic testing, and state testing -
can eliminate requirements & specifications
bugs.

2.Structural Bugs
 we look at the 5 types, their causes and
remedies.
 Control & Sequence bugs
 Logic Bugs
 Processing bugs
 Initialization bugs
 Data flow bugs & anomalies

Control & Sequence Bugs:
 Paths left out, unreachable code, spaghetti code,
and pachinko code.
 Improper nesting of loops, Incorrect loop-
termination or look-back, ill-conceived switches.
 Missing process steps, duplicated or unnecessary
processing, rampaging GOTOs.
 Old code (assembly language(ALP) & Cobol)
 Most of the control flow bugs are easily tested and
caught in unit testing.
 Prevention and Control:
 Theoretical treatment and,
 Unit, structural, path, & functional testingUnit, structural, path, & functional testing.

Logic Bugs
 Misunderstanding of the semantics of the control structures & logic
operators
 Improper layout of cases, including impossible & ignoring necessary
cases,
 Using a look-alike operator, improper simplification, confusing Ex-OR
with inclusive OR.
 Deeply nested conditional statements & using many logical operations
in 1 stmt.
 Prevention and Control:
 Logic testing, careful checks, functional testing

Processing Bugs
 Arithmetic, algebraic, mathematical function
evaluation, algorithm selection & general.
processing, data type conversion, ignoring
overflow, improper use of relational
operators.
 Prevention
 Caught in Unit TestingUnit Testing
 Domain testingDomain testing methods

Initialization Bugs
 Forgetting to initialize work space, registers, or data
areas.
 Wrong initial value of a loop control parameter.
 Accepting a parameter without a validation check.
 Initialize to wrong data type or format.
 Remedies (prevention & correction)(prevention & correction)
 Programming tools, Explicit declaration & type checking in
source language, preprocessors.
 Data flow test methods help design of tests and debugging.

Dataflow Bugs & Anomalies
 Run into an un-initialized variable.
 Not storing modified data.
 Re-initialization without an intermediate use.
 Detected mainly by execution (testing).
 Remedies (prevention & correction)(prevention & correction)
 Data flow testing methods & matrix based testing
methods.

Data BugsData Bugs
Depend on the types of data or the representation of data. There are
4 sub categories.
1. Generic Data Bugs
2. Dynamic Data Vs Static Data
3. Information, Parameter, and Control Bugs
4. Contents, Structure & Attributes related Bugs

Generic Data Bugs
– Due to data object specs., formats, # of objects & their initial
values.
– Common as much as in code, especially as the code migrates to
data.
– Data bug introduces an operative statement bug & is harder to find.
– Generalized components with reusability – when customized
from a large parametric data to specific installation.
Remedies (prevention & correction)(prevention & correction):
Using control tables in lieu of code facilitates software to handle many
transaction types with fewer data bugs. Control tables have a
hidden programming language in the database.
Caution - there’s no compiler for the hidden control language in data
tables

Dynamic Data Vs Static Data
Dynamic Data BugsDynamic Data Bugs Static Data BugsStatic Data Bugs
Transitory. Difficult to catch. Fixed in form & content.
Due to an error in a shared storage object
initialization.
Appear in source code or data base, directly or
indirectly
Due to unclean / leftover garbage in a shared
resource.
Software to produce object code creates a static
data table – bugs possible
Examples Examples
Generic & shared variable Telecom system software: generic parameters, a
generic large program & site adapter program to
set parameter values, build data declarations etc.
Shared data structure Postprocessor : to install software packages.
Data is initialized at run time – with configuration
handled by tables.
Prevention
Data validation, unit testing
Prevention
Compile time processing
Source language features

Information, Parameter, and Control Bugs
– Static or dynamic data can serve in any of the three forms. It is a matter
of perspective.
– What is information can be a data parameter or control data else where
in a program.
– Examples: name, hash code, function using these.
– A variable in different contexts.
– Information:Information: dynamic, local to a single transaction or task.
– ParameterParameter: parameters passed to a call.
– ControlControl: data used in a control structure for a decision.
Preventive MeasuresPreventive Measures (prevention & correction)(prevention & correction)
Proper Data validation code

Contents, Structure & Attributes related Bugs
 ContentsContents: are pure bit pattern & bugs are due to misinterpretation or
corruption of it.
 StructureStructure: Size, shape & alignment of data object in memory. A structure may
have substructures.
 AttributesAttributes: Semantics associated with the contents (e.g. integer, string,
subroutine).
 BugsBugs
 Severity & subtlety increases from contents to attributes as they get less
formal.
 Structural bugs may be due to wrong declaration or when same contents are
interpreted by multiple structures differently (different mapping).
 Attribute bugs are due to misinterpretation of data type, probably at an
interface

 Preventive MeasuresPreventive Measures (prevention & correction)(prevention & correction)
 Good source lang. documentation & coding style (incl. datadata
dictionarydictionary).
 Data structures be globally administered. Local data migrates to
global.
 Strongly typed languages prevent mixed manipulation of data.
 In an assembly lang. program, use field-access macros & not
directly accessing any field.

 Coding BugsCoding Bugs
 Coding errors create other kinds of bugs.
 Syntax errors are removed when compiler checks syntax.
 Coding errors
 typographical, misunderstanding of operators or statements or
could be just arbitrary.
 Documentation Bugs
 Erroneous comments could lead to incorrect maintenance.
 Testing techniques cannot eliminate documentation bugs.
 Solution:

 Inspections, QA, automated data dictionaries & specification
systems.

 Interface, Integration and Systems BugsInterface, Integration and Systems Bugs
 There are 9 types of bugs of this type.
1.1. External InterfacesExternal Interfaces
2.2. Internal InterfacesInternal Interfaces
3.3. Hardware Architecture BugsHardware Architecture Bugs
4.4. Operating System BugsOperating System Bugs
5.5. Software architecture bugsSoftware architecture bugs
6.6. Control & Sequence bugsControl & Sequence bugs
7.7. Resource management bugsResource management bugs
8.8. Integration bugsIntegration bugs
9.9. System bugsSystem bugs

1.1. External InterfacesExternal Interfaces
 Means to communicate with the world: drivers, sensors, input terminals,
communication lines.
 Primary design criterion should be - robustness.
 Bugs: invalid timing, sequence assumptions related to external signals,
misunderstanding external formats and no robust coding.
 Domain testing, syntax testing & state testing are suited to testing external
interfaces.
2.2. Internal InterfacesInternal Interfaces
 Must adapt to the external interface.
 Have bugs similar to external interface
 Bugs from improper
 Protocol design, input-output formats, protection against corrupted data,
subroutine call sequence, call-parameters.
 Remedies (prevention & correction)Remedies (prevention & correction):
 Test methods of domain testing & syntax testing.
 Good design & standards: good trade off between # of internal interfaces &
complexity of the interface.
 Good integration testing is to test all internal interfaces with external world.

 Hardware Architecture Bugs:Hardware Architecture Bugs:
 A s/w programmer may not see the h/w layer / architecture.
 S/w bugs originating from hardware architecture are due to
misunderstanding of how h/w works.
 Bugs are due to errors in:Bugs are due to errors in:
 Paging mechanism, address generation
 I/O device instructions, device status code, device protocol
 Expecting a device to respond too quickly, or to wait for too long
for response, assuming a device is initialized, interrupt
handling, I/O device address
 H/W simultaneity assumption, device data format error etc..

 Good software programming & Testing.
 Centralization of H/W interface software.
 Nowadays hardware has special test modes & test instructions
to test the H/W function.
 An elaborate H/W simulator may also be used.

 Operating System Bugs:Operating System Bugs:
 Due to:Due to:
 Misunderstanding of H/W architecture & interface by the O. S.
 Not handling of all H/W issues by the O. S.
 Bugs in O. S. itself and some corrections may leave quirks.
 Bugs & limitations in O. S. may be buried some where in the documentation.
 Same as those for H/W bugs.
 Use O. S. system interface specialists
 Use explicit interface modules or macros for all O.S. calls.
 The above may localize bugs and make testing simpler.

Software Architecture Bugs:Software Architecture Bugs: (called Interactive)
The subroutines pass thru unit and integration tests without detection of these
bugs. Depend on the Load, when the system is stressed. These are the
most difficult to find and correct.
Due to:Due to:
– Assumption that there are no interrupts, Or, Failure to block or unblock
an interrupt.
– Assumption that code is re-entrant or not re-entrant.
– Bypassing data interlocks, Or, Failure to open an interlock.
– Assumption that a called routine is memory resident or not.
– Assumption that the registers and the memory are initialized, Or, that
their content did not change.
– Local setting of global parameters & Global setting of local parameters.
RemediesRemedies:
Good design for software architecture.
Test TechniquesTest Techniques
All test techniques are useful in detecting these bugs, Stress tests in

Control & Sequence Bugs:Control & Sequence Bugs:
Due to:Due to:
– Ignored timing
– Assumption that events occur in a specified sequence.
– Starting a process before its prerequisites are met.
– Waiting for an impossible combination of prerequisites.
– Not recognizing when prerequisites are met.
– Specifying wrong priority, Program state or processing level.
– Missing, wrong, redundant, or superfluous process steps.
RemediesRemedies:
– Good design.
– highly structured sequence control - useful
– Specialized internal sequence-control mechanisms such as an internal job
control language – useful.
– Storage of Sequence steps & prerequisites in a table and interpretive
processing by control processor or dispatcher - easier to test & to correct
bugs.
Path testing as applied to Transaction Flow graphs is effective.

Resource Management Problems:Resource Management Problems:
Resources: Internal: Memory buffers, queue blocks etc. External: discs etc.
Due to:Due to:
– Wrong resource used (when several resources have similar structure or
different kinds of resources in the same pool).
– Resource already in use, or deadlock
– Resource not returned to the right pool, Failure to return a resource.
Resource use forbidden to the caller.
RemediesRemedies:
– Design: keeping resource structure simple with fewest kinds of resources,
fewest pools, and no private resource mgmt.
– Designing a complicated resource structure to handle all kinds of
transactions to save memory is not right.
– Centralize management of all resource pools thru managers, subroutines,
macros etc.
Path testing, transaction flow testing, data-flow testing & stress testing.

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