This document discusses different classes of defects that can occur during software development and testing. It identifies four main defect classes: 1. Requirement/specification defects that occur early in ambiguous, incomplete, or contradictory requirements documents. 2. Design defects that happen when system components or their interactions are incorrectly designed, such as flaws in algorithms, control logic, or interface descriptions. 3. Coding defects resulting from errors implementing code, including issues with algorithms, control structures, data types, interfaces, and documentation. 4. Testing defects in test harnesses, cases, and procedures that could lead to incorrect or incomplete testing. The classes of defects guide strategies for test planning and design.

1. IT 8076 Software Testing
UNIT – I Part -3
Dr. S. Roselin Mary,
Professor & Head
Department of Computer Science and Engineering
(NBA Accredited)
Anand Institute of Higher Technology, Chennai

2. Defect Classes :
• Important – adapt a single classification scheme & apply it to all projects
• Some defects will fit into more than one class or category – developers, testers &
SQA – try to be consistent when recording defect data
• Defect types & frequency of occurrence  guide test planning & test design
• Execution based testing strategies – strongest possibilities of detecting particular
types of defect
• Tests for new & modified software – designed to detect the most frequently
occurring defects
• Defect classes focusing execution based testing:
» Requirement/specification defect class
- Design defect class
- Coding defect class
- Testing defect class12/14/2019 2Dr.S.Roselin Mary, HOD/CSE

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DR.S.ROSELIN MARY, PROFESSOR &
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4. 1. Requirement / specification Defect classes:
• Defects injected in early phase persist & very tough to remove at later phases
• Requirement document
– written in natural language with specification
– Occurrence of ambiguous, contradictions, unclear, redundant &imprecise requirements
• Specification document – similar
– format specification language with tools
– to prevent incorrect description of system behavior
 Functional Description defects –
overall description of what the system does & how the system should behave is incorrect, ambiguous
& incomplete
 Feature defects
– feature descriptions – missing, incorrect, incomplete superfluous
– Distinguishing character of a software component/system
 Feature Interaction defects
– incorrect description of how the features should interact
– Explain the example
 Interface description defects
– defects that occur in the description of how the target software is to interface with external
hardware, software & users
• Blackbox based testing – at unit, integration, system & acceptance levels
• Feature interaction & Interface description defects – detected using BB test at integration & system level
tests
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5. 2. Design defects:
• Occur when system components, interaction between component to
component, component to outside software/hardware are incorrectly
designed
• Covers defects in design of algorithm, control, logic, data elements, module
interface description
• Detailed design description – at pseudo level with processing steps, data
structures, input output parameters & control structures
 Algorithmic & Processing defects:
– Processing steps – incorrect
– Calculation – not in order – missing/duplicated
– Algorithm reuse – chosen an inappropriate algorithm
 Control, logic & sequence defects
– Control defects occur when logic flow – incorrect
– Branching – soon, late, incorrect
– Unreachable psuedocode, improper nesting, improper procedure calls
– Incorrect use of logic operators < , >, Boolean expression in branching operation
 Data defects
– Incorrect design of data structures
– Record – lacking a field, incorrect type for variable in record
– Array – not have proper number of elements assigned
– Reviews/data dictionary – reveal these defects
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6.  Module Interface description defects
– Incorrect/inconsistent parameter types
– Incorrect number of parameters/ ordering of parameters
 Functional description defects
– Design maynot properly describe the functionality of a module
– Incorrect/missing/unclear design elements
– Detected during design review
 External Interface description defects
– Incorrect design descriptions for interfaces external software, database & hardware
devices
– Improper sequence of commands, lack of proper messages & feedback messages
3. Coding defects
• From errors in implementing the code
• Closely related to design defect classes
• Not understanding programming constructs
• Transcription/omission
 Algorithmic & Processing defects
– Unchecked overflow, underflow conditions
– Comparing inappropriate data types
– Conversion of datatype
– Precedence of operators
– Misuse of parentheses
– Incorrect use of signs12/14/2019 6Dr.S.Roselin Mary, HOD/CSE

7.  Control, logic and sequence defects
– Case statements , iteration of loops, missing paths
 Typographical defects –syntax error
 Initialization defects – omission / incorrect initialization statements
 Dataflow defects
– Variable should be initialized before its use
– Don’t initialize twice before intermediate use
 Data defects
– Incorrect implementation of data structures
– record, array, flags, indices & constant sets
 Module Interface defects – similar to design defects
 Code documentation defects
– Code documentation – doesn’t reflect what the program actually does
– Incomplete/ ambiguous/incorrect/out of date
 External hardware, software interface defects
– System calls, links to database, input output sequences, memeory usage, resource
usage, interrupts, protocols & interfaces with build files
• Design & coding defects – whitebox testing – dataflow, control, logic
– Blackbox testing – decision tables, Boolean expression
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8. 4. Testing defects
• Defects in test plan, test cases, test harnesses,
procedures
Test Hareness defect
– Test hareness / Scaffolding code – auxiliary code
developed to test the software at the unit and integration
levels
– Should be carefully designed & tested – reuse
– Subject to all other types of defects
Test case design/ Test procedure defects
– Incorrect/incomplete, missing, inappropriate test cases &
procedures
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