Se unit 4

UNIT 4 SYLLABUS
• Testing Strategies : A strategic approach to
software testing, test strategies for conventional
software, Black-Box and White-Box testing,
Validation testing, System testing, the art of
Debugging.
• Product metrics : Software Quality, Metrics for
Analysis Model, Metrics for Design Model,
Metrics for source code, Metrics for testing,
Metrics for maintenance.
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A strategic Approach for Software testing
• Software Testing
One of the important phases of software
development
Testing is the process of execution of a
program with the intention of finding errors
Involves 40% of total project cost
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• Testing Strategy
 A road map that incorporates test planning, test
case design, test execution and resultant data
collection and execution
 Validation refers to a different set of activities
that ensures that the software is traceable to the
customer requirements.
 V&V encompasses a wide array of Software
Quality Assurance
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• Perform Formal Technical reviews(FTR) to
uncover errors during software
development
• Begin testing at component level and
move outward to integration of entire
component based system.
• Adopt testing techniques relevant to
stages of testing
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• Testing can be done by software
developer and independent testing group
• Testing and debugging are different
activities. Debugging follows testing
• Low level tests verifies small code
segments.
• High level tests validate major system
functions against customer requirements
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Testing Strategies for Conventional
Software
1)Unit Testing
2)Integration Testing
3)Validation Testing and
4)System Testing
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Software Testing
• Two major categories of software testing
Black box testing
White box testing
Black box testing
Treats the system as black box whose
behavior can be determined by studying
its input and related output
Not concerned with the internal structure
of the program
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Black Box Testing
• It focuses on the functional requirements
of the software ie it enables the sw
engineer to derive a set of input conditions
that fully exercise all the functional
requirements for that program.
• Concerned with functionality and
implementation
1)Graph based testing method
2)Equivalence partitioning
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Equivalence partitioning
Example
• Input consists of 1 to 10
• Then classes are n<1,1<=n<=10,n>10
• Choose one valid class with value within
the allowed range and two invalid classes
where values are greater than maximum
value and smaller than minimum value.
16
Orthogonal array Testing
• To problems in which input domain is
relatively small but too large for exhaustive
testing
Example
• Three inputs A,B,C each having three
values will require 27 test cases
• L9 orthogonal testing will reduce the
number of test case to 9 as shown below
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Orthogonal array Testing
A B C
1 1 1
1 2 2
1 3 3
2 1 3
2 2 3
2 3 1
3 1 3
3 2 1
3 3 2
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White Box testing
• Also called glass box testing
• Involves knowing the internal working of a
program
• Guarantees that all independent paths will
be exercised at least once.
• Exercises all logical decisions on their true
and false sides
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Basis path testing
• Steps of Basis Path Testing
1.Draw the flow graph from flow chart of the
program
2.Calculate the cyclomatic complexity of the
resultant flow graph
3.Prepare test cases that will force
execution of each path
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Basis path testing
• Three methods to compute Cyclomatic
complexity number
1.V(G)=E-N+2(E is number of edges, N is
number of nodes
2.V(G)=Number of regions
3.V(G)= Number of predicates +1
25

Control Structure testing
• Basis path testing is simple and effective
• It is not sufficient in itself
• Control structure broadens the basic test
coverage and improves the quality of white
box testing
• Condition Testing
• Data flow Testing
• Loop Testing
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Condition Testing
--Exercise the logical conditions contained in a
program module
--Focuses on testing each condition in the program
to ensure that it does contain errors
--Simple condition
E1<relation operator>E2
--Compound condition
simple condition<Boolean operator>simple
condition
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Data flow Testing
• Def(definition):definition of a variable on
the left-hand side of an assignment
statement
• C- use: Computational use of a variable
like read, write or variable on the right
hand of assignment statement
• P- use: Predicate use in the condition
• Every DU chain be tested at least once.
29
Loop Testing
• Focuses on the validity of loop constructs
• Four categories can be defined
1.Simple loops
2.Nested loops
3.Concatenated loops
4.Unstructured loops
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Loop Testing
• Testing of simple loops
-- N is the maximum number of allowable
passes through the loop
1.Skip the loop entirely
2.Only one pass through the loop
3.Two passes through the loop
4.m passes through the loop where m>N
5.N-1,N,N+1 passes the loop
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Loop Testing
Nested Loops
1.Start at the innermost loop. Set all other
loops to maximum values
2.Conduct simple loop test for the
innermost loop while holding the outer
loops at their minimum iteration
parameter.
3.Work outward conducting tests for the
next loop but keeping all other loops at
minimum.
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Loop Testing
Concatenated loops
• Follow the approach defined for simple
loops, if each of the loop is independent of
other.
• If the loops are not independent, then
follow the approach for the nested loops
Unstructured Loops
• Redesign the program to avoid
unstructured loops
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Validation Testing
• It succeeds when the software functions in a
manner that can be reasonably expected by the
customer.
1)Validation Test Criteria
2)Configuration Review
3)Alpha And Beta Testing
34

System Testing
• Its primary purpose is to test the complete
software.
1)Recovery Testing
2)Security Testing
3Stress Testing and
4)Performance Testing
35
The Art of Debugging
• Debugging occurs as a consequences of
successful testing.
• Debugging Stratergies
1)Brute Force Method.
2)Back Tracking
3)Cause Elimination and
4)Automated debugging
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39
The Art of Debugging
The Debugging process
Test
cases
Execution of
test cases
Results
Debugging
Suspected
causes
Additional
tests
Identified
causes
Corrections
Regression tests
Software Quality
• Conformance to explicitly stated functional and
performance requirements, explicitly documented
development standards, and implicit characteristics that
are expected of all professionally developed software.
• Factors that affect software quality can be categorized in
two broad groups:
1. Factors that can be directly measured (e.g. defects
uncovered during testing)
2. Factors that can be measured only indirectly (e.g.
usability or maintainability)
40

Software Quality
• McCall’s quality factors
1.Product operation
a. Correctness
b. Reliability
c. Efficiency
d. Integrity
e. Usability
2.Product Revision
a. Maintainability
b. Flexibility
c. Testability 41
Software Quality
3. Product Transition
a. Portability
b. Reusability
c. Interoperability
ISO 9126 Quality Factors
1.Functionality
2.Reliability
3.Usability
4.Efficiency
5.Maintainability
6.Portability
42

43
Product metrics
• Product metrics for computer software helps us to
assess quality.
• Measure
-- Provides a quantitative indication of the extent, amount,
dimension, capacity or size of some attribute of a
product or process
• Metric(IEEE 93 definition)
-- A quantitative measure of the degree to which a system,
component or process possess a given attribute
• Indicator
-- A metric or a combination of metrics that provide insight
into the software process, a software project or a product
itself
44

Product Metrics for analysis,Design,Test
and maintenance
• Product metrics for the Analysis model
Function point Metric
 First proposed by Albrecht
 Measures the functionality delivered by the
system
 FP computed from the following
parameters
1) Number of external inputs(EIS)
2) Number external outputs(EOS) 45
Metrics for Design Model
• DSQI(Design Structure Quality Index)
• US air force has designed the DSQI
• Compute s1 to s7 from data and
architectural design
• S1:Total number of modules
• S2:Number of modules whose correct
function depends on the data input
• S3:Number of modules whose function
depends on prior processing
• S4:Number of data base items 48

• S5:Number of unique database items
• S6: Number of database segments
• S7:Number of modules with single entry
and exit
• Calculate D1 to D6 from s1 to s7 as
follows:
• D1=1 if standard design is followed
otherwise D1=0
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• D2(module independence)=(1-(s2/s1))
• D3(module not depending on prior
processing)=(1-(s3/s1))
• D4(Data base size)=(1-(s5/s4))
• D5(Database compartmentalization)=(1-
(s6/s4)
• D6(Module entry/exit characteristics)=(1-
(s7/s1))
• DSQI=sigma of WiDi 50

METRIC FOR SOURCE CODE
• HSS(Halstead Software science)
• Primitive measure that may be derived after the
code is generated or estimated once design is
complete
• n1 = the number of distinct operators that appear
in a program
• n2 = the number of distinct operands that appear
in a program
• N1 = the total number of operator occurrences.
• N2 = the total number of operand occurrence.
• Overall program length N can be computed:
• N = n1 log2 n1 + n2 log2 n2
• V = N log2 (n1 + n2) 52
METRIC FOR TESTING
• n1 = the number of distinct operators that appear in a
program
• n2 = the number of distinct operands that appear in a
program
• N1 = the total number of operator occurrences.
• N2 = the total number of operand occurrence.
• Program Level and Effort
• PL = 1/[(n1 / 2) x (N2 / n2 l)]
• e = V/PL
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METRICS FOR MAINTENANCE
• Mt = the number of modules in the current release
• Fc = the number of modules in the current release that
have been changed
• Fa = the number of modules in the current release that
have been added.
• Fd = the number of modules from the preceding release
that were deleted in the current release
• The Software Maturity Index, SMI, is defined as:
• SMI = [Mt – (Fc + Fa + Fd)/ Mt ]
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