# SE 4367 Functional Testing - PowerPoint PPT Presentation

PPT – SE 4367 Functional Testing PowerPoint presentation | free to view - id: 9171-NjNmZ The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
Title:

## SE 4367 Functional Testing

Description:

### How to generate test inputs? ... When test inputs are generated using functional specifications, we say that we ... is that if one test input in this sub ... – PowerPoint PPT presentation

Number of Views:156
Avg rating:3.0/5.0
Slides: 55
Provided by: ValuedGate1420
Category:
Tags:
Transcript and Presenter's Notes

Title: SE 4367 Functional Testing

1
SE 4367 Functional Testing
2
Learning Objectives
• What is functional testing?
• How to perform functional testing?
• How to generate test inputs?
• What are equivalence partitioning, boundary value
testing, domain testing, state testing, and
decision table testing?

3
What is Functional Testing?
• When test inputs are generated using functional
specifications, we say that we are doing
functional testing.
• Functional testing tests how well a program meets
the functionality requirements.

4
The Methodology
• The derivation of test inputs is based on
functional specifications.
• Clues are obtained from the specifications.
• Clues lead to test requirements.
• Test requirements lead to test specifications.
• Test specifications are then used to actually
execute the program under test.

5
Test Methodology
Specifications
Program output is correct
6
Equivalence Partitioning
• The input domain is usually too large for
exhaustive testing.
• It is therefore partitioned into a finite number
of sub-domains 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.

7
Equivalence Partitioning
Four test inputs, one selected from each
sub-domain.
Too many test inputs.
8
How to partition?
• Inputs to a program provide clues to partitioning.
• Example 1
• Suppose that program P takes an integer X as
input X.
• For XT1 and for X0 task T2.

9
How to partition? (contd.)
• 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
• Similarly, we expect P to perform the same way
for all values of X0.
• We therefore partition the input domain of P into
two sub-domains.

10
Two sub-domains
All test inputs in the Xconsidered 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 X0 sub-domain
also.
11
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.

12
Non-overlapping Partitions
• An equivalence class is considered covered when
at least one test has been selected from it.
• In partition testing our goal is to cover all
equivalence classes.

13
Overlapping Partitions
• Example 2
• Suppose that program P takes three integers X, Y
and Z. It is known that
• X
• ZY

14
Overlapping partitions
15
Overlapping Partition-Test Selection
• In this example, we could select 4 test cases as
• X4, Y7, Z1 satisfies X
• X4, Y2, Z1 satisfies XY
• X1, Y7, Z9 satisfies ZY
• X1, Y7, Z2 satisfies Z
• Thus, we have one test case from each equivalence
class.

16
Overlapping Partitions-Test Selection
• However, we may also select only 2 test inputs
and satisfy all four equivalence classes
• X4, Y7, Z1 satisfies X
• X4, Y2, Z3 satisfies XY and ZY
• Thus, we have reduced the number of test cases
from 4 to 2 while covering each equivalence class.

17
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.

18
Partitioning using non-numeric data
lc Lower case character UC Upper case
character null null string.
19
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

20
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
• a
• Xb (the invalid cases)

21
Guidelines (contd.)
• 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.

22
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.
approach!

23
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
X0 is a boundary. Inputs to the program might
lie on the boundary or on either side of the
boundary.

24
BVA (contd.)
• This leads to 3 test inputs
• X0, X-20, and X14.

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 (X0), the other two are large!

25
BVA (contd.)
• Now suppose that a program takes two integers X
and Y and that x1

26
BVA (contd.)
• 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)

27
BVA (contd.)
• 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?

28
BVA (contd.)
• 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)
• Can you derive the test cases using BVA?

29
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.

30
Finite State Machines (FSMs)
• A state machine is an abstract representation of
actions taken by a program or anything else that
functions!
• It is specified as a quintuple
• A a finite input alphabet
• Q a finite set of states
• q0 initial state which is a member of Q.

31
FSMs (contd.)
• T state transitions which is a mapping
• Q x A-- Q
• F A finite set of final states, F is a subset of
Q.
• Example Here is a finite state machine that
recognizes integers ending with a carriage return
character.
• A0,1,2,3,4,5,6,7,8,9, CR
• Qq0,q1,q2
• q0 initial state

32
FSMs (contd.)
• T ((q0,d),q1),(q1,d),q1), (q1,CR),q2)
• F q2
• A state diagram is an easier to understand
specification of a state machine. For the above
machine, the state diagram appears on the next
slide.

33
State diagram
d denotes a digit
34
State Diagram-Actions
x/y x is an element of the alphabet and y is an
action.
d/iid10j jj1
d/ i d j 1
CR/output i
i is initialized to d and j to 1 when the machine
moves from state q0 to q1. i is incremented by
10jd and j by 1 when the machine moves from q1
to q1. The current value of i is output when a CR
is encountered.
Can you describe what this machine computes?
35
State Machine Languages
• Each state machine recognizes a language.
• The language recognized by a state machine is the
set S of all strings such that
• when any string s in S is input to the state
machine the machine goes through a sequence of
transitions and ends up in the final state after
having scanned all elements of s.

36
State diagram-Errors
d/iid10j jj1
d/ i d j 1
CR/output I
CR/output error
reset
q4
q4 has been added to the set of states. It
represents an error state. Notice that reset is a
new member added to the alphabet.
37
State Diagram-Code
• A state diagram can be transformed into a program
using case analysis. Let us look at a C program
fragment that embodies logic represented by the
previous state diagram.
• There is one function for each action.
• digit is assumed to be provided by the lexical
analyzer.

38
Program for integer state machine
/ state is global, with values q0, q1, q2. i is
also global./
void event_digit()
• case q0
• idigit j 1 / perform action. /
• stateq1 / set next state. /
• break / event digit is done. /
• case q1
• ii10jdigit j / Add the next digit. /
• stateq1
• break
• /complete the program. /

switch (state)
39
Checking State Diagrams
• Unreachable state One that cannot be reached
from q0 using any sequence of transitions.
• Dead state One that cannot be left once it is
reached.

40
Test Requirements
• Every state must be reached at least once, Obtain
100 state coverage.
• Every transition must be exercised at least once.
Obtain 100 transition coverage.

41
Example Test Requirements
• For the integer state machine
• state machine transitions
• event digit in state q0
• event CR in state q0
• event digit in state q1
• event CR in state q1
• event reset in state q4

42
More testing of state machines?
• Yes, it is possible!
• When we learn about path coverage we will discuss
how more test requirements can be derived from a
state diagram.

43
Test Specifications
• As before, test specifications are derived from
test requirements.
• In the absence of dead states, all states and
transitions might be reachable by one test.
• It is advisable not to test the entire machine
with one test case.

44
Decision Tables
• Requirements of certain programs are specified by
decision tables.
• A decision table is useful when specifying
complex decision logic

45
Decision Tables
• A decision table has two parts
• condition part
• action part
• The two together specify under what condition
will an action be performed.

46
Decision Table-Nomenclature
• C denotes a condition
• A denotes an action
• Y denotes true
• Ndenotes false
• X denotes action to be taken.
• Blank in condition denotes dont care
• Blank in action denotes do not take the action

47
Bank Example
• Consider a bank software responsible for debiting
from an account. The relevant conditions and
actions are
• C1 The account number is correct
• C2 The signature matches
• C3 There is enough money in the account
• A1 Give money
• A2 Give statement indicating insufficient funds
• A3 Call vigilance to check for fraud!

48
Decision tables
49
Example (contd.)
• A1 is to be performed when C1, C2, and C3 are
true.
• A2 is to be performed when C1 and C2 are true and
C3 is false.
• A3 is to be performed when C1 is true and C2 is
false.

50
Default Rules
• Are all possible combinations of conditions
covered?
• No! Which ones are not covered?
• We need a default action for the uncovered
combinations. A default action could be an error
report or a reset.

51
Example-Test Requirements
• Each column is a rule and corresponds to at
least one test requirement.
• If there are n columns then there are at least n
test requirements.
• What is the maximum number of test requirements?

52
Example-Test Specifications
• For each test requirement find a set of input
values of variables such that the selected rule
is satisfied.
• When this test is input to the program the output
must correspond to the action specified in the
decision table.
• Should the testing depend on the order in which
the conditions are evaluated?

53
Summary-continued
Number of test cases
high
low
Sophistication
Boundary Value
Equivalence Class
Decision Table
54
Summary-continued
Effort to Identify Test Cases
high
low
Sophistication
Boundary Value
Equivalence Class
Decision Table