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©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 1

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Component testing
Integration testing
• Includes integration of subsystems, of systems, acceptance testing
In OO development, boundary is less clear
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 4

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The goal of defect testing is to discover defects in programs
A successful defect test is a test which causes a program to behave in an anomalous way
Tests show the presence not the absence of defects
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 6

Design test cases
Test cases
Prepare test data
Test data
Run program with test data
Test results
Compare results to test cases
Test reports
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 7

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An approach to testing where the program is considered as a ‘black-box’
The program test cases are based on the system specification
Test planning (developing test cases) can begin early in the software process
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 10

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Input data and output results often fall into different classes where all members of a class are related
Each of these classes is an equivalence partition where the program behaves in an equivalent way for each class member
Test cases should be chosen from each partition
Slide 12 ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20

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Partition system inputs and outputs into
‘equivalence sets’
• If input is a 5-digit integer between 10,000 and 99,999, equivalence partitions are <10,000, 10,000-99, 999 and >
100, 000
Choose test cases around the midpoint of partitions and at the boundary of these sets
• 5000,50000,150000
• 00000, 09999, 10000, 99999, 100000
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 14

3
4 7 10
11
Less than 4 Between 4 and 10
Number of input values
9999
10000 50000
More than 10
100000
99999
Less than 10000
Input values
©Ian Sommerville 2000
Between 10000 and 99999 More than 99999
Software Engineering, 6th edition. Chapter 20 Slide 15

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Inputs which conform to the pre-conditions
Inputs where a pre-condition does not hold
Inputs where the key element is a member of the array
Inputs where the key element is not a member of the array
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 17

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Test software with sequences which have only a single value
Use sequences of different sizes in different tests
Derive tests so that the first, middle and last elements of the sequence are accessed
Spec doesn’t say that the sequence is ordered, so don’t assume that it is
Slide 18 ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20

Array
Single value
Single value
More than 1 value
More than 1 value
More than 1 value
More than 1 value
Eleme nt
In sequence
Not in sequence
First element in sequence
Last element in sequence
Middle eleme nt in sequence
Not in sequence
Inp ut sequence (
T
)
17
17
17, 29, 21, 23
41, 18, 9, 31, 30, 16, 45
17, 18, 21, 23, 29, 41, 38
21, 23, 29, 33, 38
©Ian Sommerville 2000
Key (
Key
) Output (
Found, L
)
17
0
17
45
23
25 true, 1 false, ??
true, 1 true, 7 true, 4 false, ??
Software Engineering, 6th edition. Chapter 20 Slide 19

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Sometime called white-box testing
Derivation of test cases according to program structure. Knowledge of the program is used to identify additional test cases
Objective is to exercise all program statements
(not all path combinations)
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 20

class BinSearch {
// This is an encapsulation of a binary s earch function that takes an array of
// ordered objects and a key a nd returns an object with 2 attributes namely
// index - the value of the array index
// found - a boolean indicating whether or not the key is in the array
// An object is returned because it is not possible in J ava to pass bas ic types by
// reference to a function and so return two values
// the key is -1 if the element is not found
{ public static void search ( int key, i nt [] elemArray, Result r ) int bottom = 0 ; int top = elemArray.length - 1 ; int mid ; r.found = fals e ; r.index = -1 ;
{ while ( bottom <= top )
{ mid = (top + bottom) / 2 ; if (elemArray [mid] == key) r.index = mid ; r.found = true ; return ;
} // if part
{ else if (elemArray [mid] < key) bottom = mid + 1 ; else top = mid - 1 ;
} // s earch
} //BinSearch
}
} //while loop
Binary search (Java)

Equivalence class boundaries
Elements < Mid Elements > Mid
Mid-point
Slide 23 ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20

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Pre-conditions satisfied, key element in array
Pre-conditions satisfied, key element not in array
Pre-conditions unsatisfied, key element in array
Pre-conditions unsatisfied, key element not in array
Key found in center, top, or bottom
Input array has a single value
Input array has an even number of values
Input array has an odd number of values
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 24

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The objective of path testing is to ensure that the set of test cases is such that each path through the program is executed at least once
The starting point for path testing is a program flow graph that shows nodes representing program decisions and arcs representing the flow of control
Statements with conditions are therefore nodes in the flow graph
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 26

bottom > top
8
9
1 while bottom <= top
2
3 if (elemArray [mid] == key
4
5
(if (elemArray [mid]< key
6
7
Binary search flow graph

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The number of tests to test all control statements equals the cyclomatic complexity
Cyclomatic complexity equals number of conditions in a program + 1
Useful if used with care. Does not imply adequacy of testing.
Although all paths are executed, all combinations of paths are not executed
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 29

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Test cases should be derived so that all of these paths are executed
1, 2, 3, 8, 9
1, 2, 3, 4, 6, 7, 2, 8, 9
1, 2, 3, 4, 5, 7, 2, 8, 9
A dynamic program analyser may be used to check that paths have been executed
Slide 30 ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20

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Tests complete systems or subsystems composed of integrated components
Integration testing should be black-box testing with tests derived from the specification
Main difficulty is localizing errors
Incremental integration testing reduces this problem
Slide 31 ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20

A
T1
A
T1
A B
T2
T2 B
T3
B C
T3
C
T4
D
Test sequence
1
©Ian Sommerville 2000
Test sequence
2
Software Engineering, 6th edition. Chapter 20
T1
T2
T3
T4
T5
Test sequence
3
Slide 32

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Top-down testing
Bottom-up testing
In practice, most integration involves a combination of these strategies
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 33

Level 1
Testing sequence
Level 2
Le vel 2 stubs
Level 1
Level 2 Le vel 2
Le vel 3 stubs
Level 2
. . .
Slide 34 ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20

Test drivers
Level N Level N Le vel N Level N Level N
Testing sequence
Test drivers
Level N–1 Level N–1 Level N–1
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 35

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Architectural validation
• Top-down integration testing is better at discovering errors in the system architecture
System demonstration
• Top-down integration testing allows a limited demonstration at an early stage in the development
Test implementation
• Often easier with bottom-up integration testing
Test observation
• Problems with both approaches. Extra code may be required to observe tests
Bottom up fits well with OO development!
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 36

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Takes place when modules or sub-systems are integrated to create larger systems
Objectives are to detect faults due to interface errors or invalid assumptions about interfaces
Particularly important for object-oriented development as objects are defined by their interfaces
Slide 37 ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20

Test cases
©Ian Sommerville 2000
A B
C
Software Engineering, 6th edition. Chapter 20 Slide 38

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Interface misuse
Interface misunderstanding
Timing errors
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 40

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Exercises the system up to and beyond its maximum design load.
Stressing the system often causes defects to come to light
Stressing the system tests failure behaviour. Systems should not fail catastrophically. Stress testing checks for unacceptable loss of service or data
Particularly relevant to distributed systems which can exhibit severe degradation as a network becomes overloaded
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 42

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The components to be tested are object classes that are instantiated as objects
Larger grain than individual functions
No obvious ‘top’ to the system for top-down integration and testing
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 43

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Testing operations associated with objects
Testing object classes
Testing clusters of cooperating objects
Testing the complete OO system
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 44

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Complete test coverage of a class involves
• Testing all operations associated with an object
• Setting and interrogating all object attributes
• Exercising the object in all possible states
Inheritance makes it more difficult to design object class tests as the information to be tested is not localized
Slide 45 ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20

WeatherStation identifier reportWeather () calibrate (instruments) test () startup (instruments) shutdown (instruments)
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Test cases are needed for all operations
Use a state model to identify state transitions for testing
Examples of testing sequences
• Shutdown  Waiting  Shutdown
• Waiting  Calibrating  Testing 
Transmitting  Waiting
• Waiting  Collecting  Waiting 
Summarising  Transmitting  Waiting
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 46

Shutdown startup () shutdown ()
Operation
Waiting calibrate () test ()
Calibrating
Testing calibration OK transmission done test complete clock
Collecting collection done
Transmitting reportWeather ()
Summarising weather summary complete
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 47

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Levels of integration are less distinct in objectoriented systems
Cluster testing is concerned with integrating and testing clusters of cooperating objects
Identify clusters using knowledge of the operation of objects and the system features that are implemented by these clusters
Slide 48 ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20

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Use-case or scenario testing
Thread testing
Object interaction testing
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 49

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Identify scenarios from use-cases and supplement these with interaction (sequence) diagrams that show the objects involved in the scenario
Consider the scenario in the weather station system where a report is generated …
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 50

©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 51

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Testing is an expensive process phase. Testing workbenches provide a range of tools to reduce the time required and total testing costs
Most testing workbenches are open systems because testing needs are organization-specific – need tools to be adaptable to your organization and project
Difficult to integrate your project with closed design and analysis workbenches
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 53

Test data generator
Source code
Dynamic analyser
Test manager
Program being tested
Test data
Test results
Specification
Oracle
Test predictions
Execution report
©Ian Sommerville 2000
Simulator
File comparator
Report generator
Software Engineering, 6th edition. Chapter 20
Test results report
Slide 54