Let us start from the V-Model

Verification Phases•Requirements analysis•System Design•Architecture Design•Module Design•Coding

Validation phases•Unit Testing•Integration Testing•System Testing•User Acceptance Testing

This model helped in realizing that Testing has to be started early in the lifecycle of software development and thus more emphasis was laid on Static Testing during the Verification Phases

Why Test Designing

•The Quality of Testing is as good as its Test Design

•Usage of formal and customized Test Specification techniques for

•deriving Test Cases from the Input Documents (Test Basis) will

•help in achieving the following:

Proper Coverage/Depth in testing each of the functions (/system)

Test Specifications prepared by various members in the test team will be uniform

Test Cases will be more Manageable

Understanding test design techniques

Classic distinction – black-box and white box techniquesBlack box - Black-box techniques (also called specification-based techniques) are a way to

derive and select test conditions or test cases based on an analysis of the test basis documentation, whether functional or non-functional, for a component or system without reference to its internal structure.

White box - White-box techniques (also called structural or structure-based techniques) are based on an analysis of the internal structure of the component or system.

Black Box White Box

Tests are derived from functional designed specifications

Tests require knowledge of the internal program structure and the code

Will fail to test “ hidden” functions Will fail to detect “missing” functions

Data driven Logic driven testing

Requires exhaustive input testing to detect all errors

Requires exhaustive Path testing to detect all errors

Categories of test design techniques

Requirement based techniques:–Models, either formal or informal, are used for the specification of the

problem to be solved, the software or its components.–From these models test cases can be derived systematically.

Structure based techniques:– Information about how the software is constructed is used to derive

the test cases, for example, code and design.–The extent of coverage of the software can be measured for existing

test cases, and further test cases can be derived systematically to increase coverage.

Black Box Testing Methodologies

Equivalence Partitioning Boundary Value Analysis Decision Table Cause Effect Graph State Transition

Equivalence PartitioningPartitioning the input domain of a program into a finite number of classes [sets], to identify a minimal set of well selected test cases to represent these classes. There are two types of input equivalence classes, valid and invalid.

Continuous equivalence classes Discrete equivalence classes

Equivalence class testing can significantly reduce the number of test cases that must be created and executed

Partitioning the input domain of a program into a finite number of classes [sets], to identify a minimal set of well selected test cases to represent these classes. There are two types of input equivalence classes, valid and invalid.

Continuous equivalence classes Discrete equivalence classes

Equivalence class testing can significantly reduce the number of test cases that must be created and executed

A module for a human resources system that decides how we should process employment applications based on a person's age.

A module for a human resources system that decides how we should process employment applications based on a person's age.

0–15 Don't hire

16–17 Can hire on a part-time basis only

18–54 Can hire as a full-time employee

55–99 Don't hire

Equivalence Partitioning continued…Normal Test Cases Test Data If (applicantAge == 0) hireStatus="NO"; 0 If (applicantAge == 1) hireStatus="NO"; 1 … … If (applicantAge == 14) hireStatus="NO"; 14 If (applicantAge == 15) hireStatus="NO"; 15 If (applicantAge == 16) hireStatus="PART"; 16 If (applicantAge == 17) hireStatus="PART"; 17 If (applicantAge == 18) hireStatus="FULL"; 18 If (applicantAge == 19) hireStatus="FULL"; 19 … … If (applicantAge == 53) hireStatus="FULL"; 53 If (applicantAge == 54) hireStatus="FULL"; 54 If (applicantAge == 55) hireStatus="NO"; 55 If (applicantAge == 56) hireStatus="NO"; 56 … … If (applicantAge == 98) hireStatus="NO"; 98 If (applicantAge == 99) hireStatus="NO"; 99

Test Cases using equivalence partition Test Data If (applicantAge >= 0 && applicantAge <=15) hireStatus="NO"; 13 If (applicantAge >= 16 && applicantAge <=17) hireStatus="PART"; 17 If (applicantAge >= 18 && applicantAge <=54) hireStatus="FULL"; 27 If (applicantAge >= 55 && applicantAge <=99) hireStatus="NO"; 75

A group of tests forms an equivalence class : They all test the same thing. If one test catches a bug, the others probably will too within each equivalence class. If one test doesn't catch a bug, the others probably won't either within each equivalence class.

Using the equivalence class approach, we have reduced the number of test cases from 100 (testing each age) to four (testing one age in each equivalence class) — a significant savings.

Normal Test Cases Test Data If (applicantAge == 0) hireStatus="NO"; 0 If (applicantAge == 1) hireStatus="NO"; 1 … … If (applicantAge == 14) hireStatus="NO"; 14 If (applicantAge == 15) hireStatus="NO"; 15 If (applicantAge == 16) hireStatus="PART"; 16 If (applicantAge == 17) hireStatus="PART"; 17 If (applicantAge == 18) hireStatus="FULL"; 18 If (applicantAge == 19) hireStatus="FULL"; 19 … … If (applicantAge == 53) hireStatus="FULL"; 53 If (applicantAge == 54) hireStatus="FULL"; 54 If (applicantAge == 55) hireStatus="NO"; 55 If (applicantAge == 56) hireStatus="NO"; 56 … … If (applicantAge == 98) hireStatus="NO"; 98 If (applicantAge == 99) hireStatus="NO"; 99

Test Cases using equivalence partition Test Data If (applicantAge >= 0 && applicantAge <=15) hireStatus="NO"; 13 If (applicantAge >= 16 && applicantAge <=17) hireStatus="PART"; 17 If (applicantAge >= 18 && applicantAge <=54) hireStatus="FULL"; 27 If (applicantAge >= 55 && applicantAge <=99) hireStatus="NO"; 75

A group of tests forms an equivalence class : They all test the same thing. If one test catches a bug, the others probably will too within each equivalence class. If one test doesn't catch a bug, the others probably won't either within each equivalence class.

Using the equivalence class approach, we have reduced the number of test cases from 100 (testing each age) to four (testing one age in each equivalence class) — a significant savings.

Boundary Value AnalysisA selection technique in which test data are chosen to lie along "boundaries“ of the input domain [or output range] classes, data structures, procedure parameters, etc. Choices often include maximum, minimum, and trivial values This technique is often called stress testing.

A selection technique in which test data are chosen to lie along "boundaries“ of the input domain [or output range] classes, data structures, procedure parameters, etc. Choices often include maximum, minimum, and trivial values This technique is often called stress testing.

ContinuousContinuous

DiscreteDiscrete

A module for a human resources system that decides how we should process employment applications based on a person's age.

A module for a human resources system that decides how we should process employment applications based on a person's age.

ExampleExample

A module for a human resources system that decides how we should process employment applications based on a person's age.

A module for a human resources system that decides how we should process employment applications based on a person's age.

0–15 Don't hire

16–17 Can hire on a part-time basis only

18–54 Can hire as a full-time employee

55–99 Don't hire

What about ages -3 and 101? Note that the requirements do not specify how these values should be treated. We could guess but "guessing the requirements" is not an acceptable practice.

What about ages -3 and 101? Note that the requirements do not specify how these values should be treated. We could guess but "guessing the requirements" is not an acceptable practice.

Boundary Value Analysis Continued…

If (applicantAge >= 0 && applicantAge <=15) hireStatus="NO"; If (applicantAge >= 16 && applicantAge <=17) hireStatus="PART";If (applicantAge >= 18 && applicantAge <=54) hireStatus="FULL"; If (applicantAge >= 55 && applicantAge <=99) hireStatus="NO";

If (applicantAge >= 0 && applicantAge <=15) hireStatus="NO"; If (applicantAge >= 16 && applicantAge <=17) hireStatus="PART";If (applicantAge >= 18 && applicantAge <=54) hireStatus="FULL"; If (applicantAge >= 55 && applicantAge <=99) hireStatus="NO";

The interesting values on or near the boundaries in this example areThe interesting values on or near the boundaries in this example are

Test DataTest Data

S. No Statement Left Epsilon

Left Extreme

Interior Right Extreme

Right Epsilon

1 applicantAge >= 0 && applicantAge <=15

-1 0 11 15 16

2 applicantAge >= 16 && applicantAge <=17

15 16 16 17 18

3 applicantAge >= 18 && applicantAge <=54

17 18 27 54 55

4 applicantAge >= 55 && applicantAge <=99

54 55 75 99 100

Select the test cases at the “edges” of Equivalence classes in addition to selecting an element in the class

Select the test cases at the “edges” of Equivalence classes in addition to selecting an element in the class

Decision TableA Test criteria to identify which actions should be produced in response to particular combinations of conditionsDerive the logic function for the model to validate its completeness and consistency

A Test criteria to identify which actions should be produced in response to particular combinations of conditionsDerive the logic function for the model to validate its completeness and consistency

Example - A Bank has the following norms fixed to provide personal loansExample - A Bank has the following norms fixed to provide personal loans

• If age <= 25 and no loan has been taken, loan will be 1 lakh else 2 lakhs• If age <= 25 and no. of loans taken is one, loan will be 50 thousands else 1.5 lakhs• If age <= 25 and no. of loans taken is two, loan will be 25 thousands else 1 lakh• If apply for third loan cancel loan approval process

• If age <= 25 and no loan has been taken, loan will be 1 lakh else 2 lakhs• If age <= 25 and no. of loans taken is one, loan will be 50 thousands else 1.5 lakhs• If age <= 25 and no. of loans taken is two, loan will be 25 thousands else 1 lakh• If apply for third loan cancel loan approval process

No. of loans already taken

Age Loan Amount Approval Status

0 <=25>=26

1 lakh2 lakhs

Yes Yes

1 <=25>=26

50 thousands1.5 lakhs

Yes Yes

2 <=25>=26

25 thousands1 lakh

Yes Yes

3 0 No, Cancel Loan

Decision Variable : Age, No. of loans

Actions : Loan Amount, Approval status

Decision Variable : Age, No. of loans

Actions : Loan Amount, Approval status

Cause Effect Graph

A graphical representation of inputs or stimuli (causes) with their associated outputs (effects), which can be used to design test cases.A systematic method of generating test cases representing combinations of conditions.The input and output domains are partitioned into classes and analysis is performed to determine which input classes cause which effect.

A graphical representation of inputs or stimuli (causes) with their associated outputs (effects), which can be used to design test cases.A systematic method of generating test cases representing combinations of conditions.The input and output domains are partitioned into classes and analysis is performed to determine which input classes cause which effect.

Example - A Bank has the following norms fixed to provide personal loansExample - A Bank has the following norms fixed to provide personal loans

• If age <= 25 and no loan has been taken, loan will be 1 lakh else 2 lakhs• If age <= 25 and no. of loans taken is one, loan will be 50 thousands else 1.5 lakhs• If age <= 25 and no. of loans taken is two, loan will be 25 thousands else 1 lakh• If apply for third loan cancel loan approval process

• If age <= 25 and no loan has been taken, loan will be 1 lakh else 2 lakhs• If age <= 25 and no. of loans taken is one, loan will be 50 thousands else 1.5 lakhs• If age <= 25 and no. of loans taken is two, loan will be 25 thousands else 1 lakh• If apply for third loan cancel loan approval process

Cause Effect Graph Continued…

Cause Effect Graph Continued…

State Transition

A test design technique in which test cases are designed to execute state transitions. Events are caused by input and Actions are likely to cause output Helpful in Web based testing

A test design technique in which test cases are designed to execute state transitions. Events are caused by input and Actions are likely to cause output Helpful in Web based testing

Transitions

State 1

State 2

inputinput

outputoutputEvent /Action

Event /Action

PT BT

UT

ST/CBST/CB

ST/CBST/CB

ST/CUST/CU

ST/CUST/CU

ExampleMS-WORD

ExampleMS-WORD

BT – Bold TextUT – Underlined TextPT – Plain TextST – Select TextCB – Click BoldCU – Click Underline

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