Input Space Partitioning in Software Testing: Modeling the Input Domain with ISP, Summaries of Software Engineering

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Introduction to Software

Testing

Chapter 6

Input Space Partition Testing

Paul Ammann & Jeff Offutt

http://www.cs.gmu.edu/~offutt/softwaretest/

Modeling the Input Domain

• Step 1 : Identify testable functions
  • Individual methods have one testable function
  • Methods in a class often have the same characteristics
  • Programs have more complicated characteristics—

modeling documents such as UML can be used to design

characteristics

• Systems of integrated hardware and software components

can use devices, operating systems, hardware platforms,

browsers, etc.

public enum Triangle { Scalene, Isosceles, Equilateral,

Invalid }

public static Triangle triang (int Side, int Side2, int Side3)

// Side1, Side2, and Side3 represent the lengths of the sides of

a triangle

// Returns the appropriate enum value

Modeling the Input Domain ( cont )

• Step 3 : Model the input domain

• The domain is scoped by the parameters
• The structure is defined in terms of characteristics
• Each characteristic is partitioned into sets of blocks
• Each block represents a set of values
• This is the most creative design step in using ISP

• Step 4 : Apply a test criterion to choose combinations of

values

• A test input has a value for each parameter
• One block for each characteristic
• Choosing all combinations is usually infeasible
• Coverage criteria allow subsets to be chosen

• Step 5 : Refine combinations of blocks into test inputs

• Choose appropriate values from each block

Two Approaches to Input Domain

Modeling

1. Interface-based approach

• Develops characteristics directly from individual input parameters
• Simplest application
• Can be partially automated in some situations

2. Functionality-based approach

• Develops characteristics from a behavioral view of the program under test
• Harder to develop—requires more design effort
• May result in better tests, or fewer tests that are as effective Input Domain Model (IDM)

1. Interface-Based Example

• Consider method triang() from class TriangleType on the

book website :

• http://www.cs.gmu.edu/~offutt/softwaretest/java/Triangle.java
• http://www.cs.gmu.edu/~offutt/softwaretest/java/TriangleType.java Introduction to Software Testing, Edition 2 (Ch 6) © Ammann & Offutt 7 public enum Triangle { Scalene, Isosceles, Equilateral, Invalid } public static Triangle triang (int Side, int Side2, int Side3) // Side1, Side2, and Side3 represent the lengths of the sides of a triangle // Returns the appropriate enum value The IDM for each parameter is identical Reasonable characteristic : Relation of side with zero

Interface-Based – triang()

• triang () has one testable function and three integer inputs

Introduction to Software Testing, Edition 2 (Ch 6) © Ammann & Offutt 12 Characteristic b 1 b 2 b 3 q 1 = “Relation of Side 1 to 0” greater than 0 equal to 0 less than 0 q 2 = “Relation of Side 2 to 0” greater than 0 equal to 0 less than 0 q 3 = “Relation of Side 3 to 0” greater than 0 equal to 0 less than 0 First Characterization of TriTyp’s Inputs

• Consider the characteristic q1 for side 1.
  • If one value is chosen from each block, we will have three

tests:

• Test 1 (side 1 = 7, to satisfy block b1)
• Test 2 (side 1 = 0, to satisfy block b2)
• Test 3 (side 1 = - 2, to satisfy block b3)

Interface-Based IDM— triang ()

Second Characterization of triang()’s Inputs Characteristic b 1 b 2 b 3 b 4 q 1 = “Refinement of q 1 ” greater than 1 equal to 1 equal to 0 less than 0 q 2 = “Refinement of q 2 ” greater than 1 equal to 1 equal to 0 less than 0 q 3 = “Refinement of q 3 ” greater than 1 equal to 1 equal to 0 less than 0

• A maximum of 444 = 64 tests

• Complete because the inputs are integers (0.. 1)

Possible values for partition q 1 Characteristic b 1 b 2 b 3 b 4 Side1 (^5) 2 (^) (^1 0) - - 1 5 Test boundary conditions

2. Functionality-Based Approach

• Identify characteristics that correspond to the intended

functionality

• Requires more design effort from tester

• Can incorporate domain and semantic knowledge

• Can use relationships among parameters

• Modeling can be based on requirements, not

implementation

• The same parameter may appear in multiple

characteristics, so it’s harder to translate values to test

cases

Functionality-Based IDM —triang ()

• Values for this partitioning can be chosen as

Possible values for geometric partition q

1 Characteristic b 1 b 2 b 3 b 4 Triangle (4, 5, 6) (3, 3, 4) (3, 3, 3) (3, 4, 8)

Functionality-Based IDM— triang ()

• A different approach would be to break the geometric

characterization into four separate characteristics

Four Characteristics for triang () Characteristic b 1 b 2 q 1 = “Scalene” True False q 2 = “Isosceles” True False q 3 = “Equilateral” True False q 4 = “Valid” True False

• Use constraints to ensure that
  • Equilateral = True implies Isosceles = True
  • Valid = False implies Scalene = Isosceles = Equilateral = False

In-Class Exercise

Introduction to Software Testing, Edition 2 (Ch 6) © Ammann & Offutt 20

Work with 2 or 3 classmates

Create two IDMs for findElement () :

1) Interface-based

2) Functionality-based

public boolean findElement (List list, Object element) // Effects: if list or element is null throw NullPointerException // else return true if element is in the list, false otherwise

Steps 1 & 2—Interface & Functionality-Based public boolean findElement (List list, Object element) // Effects: if list or element is null throw NullPointerException // else return true if element is in the list, false otherwise Interface-Based Approach Two parameters : list, element Characteristics : list is null (block1 = true, block2 = false) list is empty (block1 = true, block2 = false) Functionality-Based Approach Two parameters : list, element Characteristics : number of occurrences of element in list (0, 1, >1) element occurs first in list (true, false) element occurs last in list (true, false)

Required Reading

• Chapter 6 from Amman’s and Offut’s book: An

Introduction to Software Testing

Introduction to Software Testing, Edition 2 (Ch 6) © Ammann & Offutt 23