Test design techniques

Test Design Techniques

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In this presentation…..

Black Box Techniques
Equivalence Partioning
Boundary Value Analysis

White Box Techniques
Basis Path Testing
Control Structure Testing
Program Technique Testing
Mutation Testing

co-sponsered by smackstuff.com

Equivalence partitioning

•The input domain is usually too large for exhaustive
testing.
•It is therefore partitioned into a finite number of subdomains for the selection of test inputs.
•Each sub-domain is known as an equivalence class and
serves as a source of at least one test input.


Equivalence partitioning
Input domain

Input domain
partitioned into four
sub-domains.
2

1
Functional testing

3
4
Too many
test inputs.

Four test inputs, one
selected from each sub-domain.


How to partition?
•

Inputs to a program provide clues to partitioning.

•

Example 1:
– Suppose that program P takes an input X, X being an integer.
– For X<0 the program is required to perform task T1 and for X>=0
task T2.

Functional testing

How to partition?-continued
– The input domain is prohibitively large because X can assume a large
number of values.
– However, we expect P to behave the same way for all X<0.
– Similarly, we expect P to perform the same way for all values of
X>=0.
– We therefore partition the input domain of P into two sub-domains .

Functional testing

Two sub-domains

One test case:
X=-3
Equivalence class

Equivalence class

X<0 X>=0

Another test case:
X=-15

Functional testing

All test inputs in the X<0 sub-domain are considered equivalent.
The assumption is that if one test input in this sub-domain reveals
an error in the program, so will the others.
This is true of the test inputs in the X>=0 sub-domain also.

Non-overlapping partitions
•

In the previous example, the two equivalence classes are non-overlapping.
In other words the two sub-domains are disjoint.

•

When the sub-domains are disjoint, it is sufficient to pick one test input
from each equivalence class to test the program .

•

An equivalence class is considered covered when at least one test has
been selected from it.

Functional testing

•

In partition testing our goal is to cover all equivalence classes.


Overlapping partitions
•

Example 2:
– Suppose that program P takes three integers X, Y and Z. It is known
that:
• X<Y
• Z>Y

Functional testing

Overlapping partitions

X<Y, Z<=Y
X=2, Y=3, Z=1

X>=Y, Z<=Y
X=15, Y=4, Z=1

X<Y
X<Y, Z>Y
X=3, Y=4, Z=7

X>=Y

Functional testing

Z>Y

Z<=Y

X>=Y, Z>Y
X=15, Y=4, Z=7

Overlapping partition-test selection
•

In this example, we could select 4 test cases as:
– X=4, Y=7, Z=1
– X=4, Y=2, Z=1

satisfies X>=Y

– X=1, Y=7, Z=9

satisfies Z>Y

– X=1, Y=7, Z=2
•

satisfies X<Y

satisfies Z<=Y

Thus, we have one test case from each equivalence class

Functional testing

.

Overlapping partition-test selection
•

However, we may also select only 2 test inputs and satisfy all four
equivalence classes:
– X=4, Y=7, Z=1
– X=4, Y=2, Z=3

•

satisfies X<Y and Z<=Y
satisfies X>=Y and Z>Y

Thus, we have reduced the number of test cases from 4 to 2 while
covering each equivalence class.

Functional testing

Partitioning using non-numeric data
•
•

In the previous two examples the inputs were integers. One can derive
equivalence classes for other types of data also.
Example 3:
– Suppose that program P takes one character X and one string Y as
inputs. P performs task T1 for all lower case characters and T2 for
upper case characters. Also, it performs task T3 for the null string
and T4 for all other strings.

Functional testing

Partitioning using non-numeric data
X: lc, Y: not null
X: UC, Y: not null
X: lc
X:UC
X: lc, Y: null
Functional testing

Y: null Y: not null

X: UC, Y: null

lc: Lower case character
UC: Upper case character
null: null string.


Non-numeric data
•
•

Once again we have overlapping partitions.
We can select only 2 test inputs to cover all four equivalence classes. These
are:
– X: lower case, Y: null string
– X: upper case, Y: not a null string

Functional testing

Guidelines for equivalence partitioning
•

Input condition specifies a range : create one for the valid case and two for
the invalid cases.
– e.g. for a<=X<=b the classes are
• a<=X<=b (valid case)
• X<a and X>b (the invalid cases)

Functional testing

Guidelines-continued
•

Input condition specifies a value: create one for the valid value and two
for incorrect values (below and above the valid value). This may not be
possible for certain data types, e.g. for Boolean.

•

Input condition specifies a member of a set: create one for the valid


value and one for the invalid (not in the set) value

Design Techniques.

.

Sufficiency of partitions
•
•
•

In the previous examples we derived equivalence classes based on the
conditions satisfied by the input data.
Then we selected just enough tests to cover each partition.
Think of the advantages and disadvantages of this approach !

Design Techniques

Boundary value analysis (BVA)
•
•
•

Another way to generate test cases is to look for boundary values.
Suppose a program takes an integer X as input.
In the absence of any information, we assume that X=0 is a boundary.
Inputs to the program might lie on the boundary or on either side of the
boundary.

Design Techniques

BVA: continued
•

This leads to 3 test inputs:
X=0, X=-20, and X=14.
Note that the values -20 and 14 are on either side of the boundary and are
chosen arbitrarily.


•

Notice that using BVA we get 3 equivalence classes. One of these three
classes contains only one value (X=0), the other two are large

Design Techniques

!

BVA: continued
•

Now suppose that a program takes two integers X and Y and that x1<=X<=x2
and y1<=Y<=y2.


y2

11

8
y1

5

1

2
10
9

12

4
x1

December 20, 2013

14

Design Techniques

13
7
x2

6
3

BVA-continued
•

In this case the four sides of the rectangle represent the boundary.

•

The heuristic for test selection in this case is:
Select one test at each corner (1, 2, 3, 4).


Select one test just outside of each of the four sides of the boundary
(5, 6, 7, 8)

Design Techniques

BVA-continued
• Select one test just inside of each of the four sides of the boundary
(10, 11, 12, 13).
• Select one test case inside of the bounded region (9).
• Select one test case outside of the bounded region (14).

How many equivalence classes do we get?

Design Techniques

BVA -continued
In the previous examples we considered only numeric data.
BVA can be done on any type of data.
For example, suppose that a program takes a string S and an integer X as inputs.
The constraints on inputs are:

length(S)<=100 and a<=X<=b

Can you derive the test cases using BVA?

Design Techniques

BVA applied to output variables
Just as we applied BVA to input data, we can apply it to output data.
Doing so gives us equivalence classes for the output domain.
We then try to find test inputs that will cover each output equivalence class.

Design Techniques

White Box Testing Techniques
It is also called as open box or clear box.
Basis Path Testing

•

•


•


•

Mutation Testing

Design Techniques

Basis Path Testing
•

Checking for the program running or not from all the possible flows

•

Generate flow graph

•

Calculate Cyclomatic complexity


Example
Program

Flow Graph
Cyclomatic complexity

1 + 1 + 1+ 1 = 4

Design Techniques

Basis Path Testing
Using this technique programmers can estimate the execution of the program without
any interruption.

•

Step1: Prepare a program with respect to program logic

•

Step2: Prepare Flow Graph of that program

•

•

Step3: Calculate cyclomatic complexity

•

Step4: Run that program more than one time to cover all the independent paths

Design Techniques

During this testing programmers validate the input and output correctness
Step1: Prepare the program according to the design logic
Step2: Execute the program

Step3: Check the input given to the program in all possible ways
Step4: Check the output of the program

Design Techniques

•

Using this technique programmers are testing the performance of the program with
different inputs

•

Step1: Prepare the program with respective design logic

•

Step2: Execute the program with different inputs

•

Step3: Calculate the process time


•

Step4: If program execution time is not acceptable change the structure of the
program without disturbing the functionality

Design Techniques

Mutation Testing
•

Programmers are making changes in the program to estimate the completeness and
correctness of the program


Program

Program

Program

Change

Change

Passed

Failed

Design Techniques

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Test design techniques

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