Test design techniques

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ISTQBTest design Techniques

Akshi Chawla20th June 2011

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Connect. Collaborate. Innovate.Agenda

Test design Techniques Static Testing Black Box Testing White Box testing Experience Based Testing Choosing a Testing Technique Q & A


Connect. Collaborate. Innovate.Test Design Techniques

Static Dynamic

Structural based

Informal ReviewInformal Review

Technical ReviewTechnical Review

WalkthroughWalkthrough

Static AnalysisStatic Analysis

InspectionInspection

Experienced Based

Data FlowData Flow

Control FlowControl Flow

Multiple ConditionMultiple Condition

ConditionCondition

ExploratoryExploratory

Error GuessingError Guessing

DecisionDecision

StatementStatement

State TransitionState Transition

Decision tableDecision table

BVABVA

EQP

Specification basedSpecification based

Use CaseUse Case


Connect. Collaborate. Innovate.Static Testing

Non Execution Technique Used to Review Documents Review Process

• Informal Review• Formal Review• Walkthrough• Technical Review• Inspection



Roles and Responsibilities1. Moderator2. Author3. Scribe4. Reviewers5. Manager

Phases of Formal Review1. Planning2. Kick Off3. Preparation4. Review Meetings5. Rework6. Follow up

Static Testing


Connect. Collaborate. Innovate.Static Analysis: Cyclomatic Complexity

Developed by Thomas J. McCabe Provide a quantitative measure of logical complexity of

program Cyclomatic complexity is computed using the control flow

graph of the program


Connect. Collaborate. Innovate.Control flow graph (CFG)

It is the way control flows through the program Three kinds of nodes:

Statement nodes: single-entry-single-exitsequences of statements

Predicate (decision) nodes: conditions forbranching

Auxiliary nodes: (optional) for easierunderstanding (e.g. “merge points” for IF)

Edges: possible flow of control


Connect. Collaborate. Innovate.How to Draw CFG

int f1(int x,int y){ 1. while (x != y){2. if (x>y) then 3. x=x-y;4. else y=y-x;5. }6. return x; }


Connect. Collaborate. Innovate.Cyclomatic complexity Definition

Cyclomatic Complexity V(G) for a graph (G) • V(G) = E-N+2

E = EdgesN=Nodes

• V(G)= P+1P= Predicate node.

• V(G) = Total number of bounded areas + 1Any region enclosed by a nodes and edge sequence.


Connect. Collaborate. Innovate.Example

The Flow Graph has 3 regionsV(G) = 2 predicate nodes +1= 3V(G) = 7edges- 6 nodes +2 = 3V(G) = 2 bounded area +1 = 3

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Connect. Collaborate. Innovate.Derivation of Test Cases

Number of independent paths: 3• 1, 6 test case (x=1, y=1)• 1, 2, 3, 5, 1, 6 test case(x=1, y=2)• 1, 2, 4, 5, 1, 6 test case(x=2, y=1)


Connect. Collaborate. Innovate.Black box testing

Focuses on Functional and Non Functional requirement

requirements

outputs

events

inputs


Connect. Collaborate. Innovate.Black Box Testing Types

Equivalence class partitioning Boundary value analysis Decision table testing State Transition


Connect. Collaborate. Innovate.Black Box - Equivalence Class Partitioning

Input values to a program are partitioned into equivalence classes. Why we do Partitioning?



A program reads an input value in the range of 1 and 5000:• computes the square root of the input number

SQRTSQRT

There are three equivalence classes: • the set of negative integers, • set of integers in the range of 1 and 5000, • integers larger than 5000.


Connect. Collaborate. Innovate.Example (cont.)

The test suite must include:• representatives from each of the three equivalence classes:• a possible test suite can be:

{-5,500,6000}.

11 50005000


Connect. Collaborate. Innovate.Black Box - Boundary Value Analysis

Some typical programming errors occur: • at boundaries of equivalence classes

Programmers often fail to see:• special processing required at the boundaries of equivalence classes.

Compute square root of an integer in the range of 1 and 5000:• test cases : {0,1,5000,5001}.

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Connect. Collaborate. Innovate.Black Box - Decision Table

A decision table is a good way to deal with combinations of things (e.g. inputs).

Known as ‘Cause-Effect' table. Testing all combinations may be impractical if not impossible How to Use Decision Table

• Identify the conditions• Identify combination of true or false. Rules = 2n (where n is number of conditions )

• Identify correct outcome for each combination• Write Test Cases based for each rule

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Connect. Collaborate. Innovate.Black Box - State Transition

It focuses on how state transition from one stage to next depending on events

In this technique state of system is first recognized and then test cases are written to test the transition from one state to another


Connect. Collaborate. Innovate.Black Box - State Transition

A website shopping basket start out as empty. As purchases are selected they are added to shopping basket. Items can also be removed from shopping basket. When the customer decides to check out , a summary of items in the basket and total cost are shown , for customer to say whether this is Ok or not. If the content and prices are Ok, then you leave summary display and go to payment system . Otherwise you go back to shopping ( so you can remove items if you want)


Connect. Collaborate. Innovate.Black Box – N-Switch Testing

0-switch coverage • Coverage of all individual transitions

l-switch coverage • Coverage of transition pairs

2-switch coverage • Coverage of transition triples is, etc.


Connect. Collaborate. Innovate.White Box Testing

Focuses on Internal Knowledge• Exercise all independent paths• exercise all logical decisions• execute all loops


Connect. Collaborate. Innovate.White Box Testing Types

Statement coverage Branch coverage Path coverage Condition coverage


Connect. Collaborate. Innovate.White Box - Statement Coverage

Methodology: • Every statement is executed at least once.

The principal idea: • unless a statement is executed, we have no way of knowing if an error

exists in that statement

Number of Statement Exercised Statement coverage = --------------------------------------------- x 100%

Total number of statements



1 READ A 2 READ B 3 C =A + 2*B 4 IF C> 50 THEN 5 PRINT large C 6 ENDIF

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Connect. Collaborate. Innovate.White Box - Branch Coverage

Test cases are designed such that:• different branch conditions is given true and false values in turn.

Branch testing guarantees statement coverage



Suppose that we write and execute two test cases Case 1: 1-2-exit Case 2: 1-2-3-4-5-7-8-2-3-4-5-7-8-2-exit

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Connect. Collaborate. Innovate.White Box -Condition Coverage

Test cases are designed such that:• each component of a composite conditional expression given both true

and false values. Example

• Consider the conditional expression ((c1and c2) or c3):• Each of c1, c2, and c3 are exercised at least once i.e. given true and

false values.

Number of Condition outcome exercised Condition coverage = ---------------------------------------------------------- x 100%

Total number of Condition outcome


Connect. Collaborate. Innovate.Branch testing Vs Condition testing

Condition testing• stronger testing than branch testing:

Branch testing • stronger than statement coverage testing.


Connect. Collaborate. Innovate.Experienced Based

Error Guessing• The success of error guessing is very much dependent on the skill of

the tester Exploratory Testing

• Is a hands-on approach in which testers are involved in minimum planning and maximum test execution.


Connect. Collaborate. Innovate.Choosing a Testing Technique

The internal factors • Tester Knowledge /Experience• Likely Defects• Test Objective• Documentation• Life Cycle Model

External Factor• Risk• Customer /contractual Requirement• Time and budget



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