In this tutorial, the program inputs the marks of five subject of 40 students and outputs average marks and the pass / fail message.

Objective of the Tutorial: To draw a Flow Graph, find its Cyclomatic Complexity, V(G) and the independent paths for a piece of code given below.


A brief Introduction to Basis Path Testing & measurement of Complexity Measure V(G):

Basis path testing helps a tester to compute logical complexity measure, V(G), of the code. This value of V(G), defines the maximum number of test cases to be designed by identifying basis set of execution paths to ensure that all statements are executed at least once.

Steps to compute the complexity measure, V(G) are as under

Step – 1: Construct the flow graph from the source code or flow charts.

Refer Following Tutorial on :

Flow Graph and its Notations

Step – 2: Identify independent paths.

Step – 3: Calculate Cyclomatic Complexity, V(G).

Step – 4: Design the test cases.

 

Objective of the Tutorial: To draw a Flow Graph, find its Cyclomatic Complexity, V(G) and the independent paths for the following piece of code.

      # include

1)  main ( ) {

2)  int num student, marks, subject total ;

3)  float average ;

4)  num_student = 1;

5) while (num_student < = 40) {

6)  total = 0 ;

7)  subject = 1;

8)  while (subject < = 5) }

9)  Scanf ("Enter marks : % d”, & marks);

10) total = total + marks ;

11) subject ++;

12) }

13) average = total/5 ;

14) if (average > = 50)

15) printf ("Pass... Average marks = % f", average);

16) else

17) print ("FAIL ... Average marks are % f”, average) ;

18) num_student ++;

19) }

20) printf ("end of program") ;

21) }

Process of constructing the flow graph:

Step – 1: Start dividing the program into parts where flow of control has single entry and exit point. In this program, line number 2 to 4 are grouped as one node (marked as 'a') only. This is because it consists of declaration and initialization of variables. The second part comprises of a while loop-outer one, from lines 5 to 19 and the third part is a single “printf” statement at line number 20.

Here the second part is again divided into four parts-statements of line 6 and 7, lines 8 to 12, line 13 and lines 14-17 i.e. “if-then-else” structure using the flow graph notation, we get this flow graph

Here, “ * '' indicates that the node is a predicate node i.e., it has an out-degree of 2.

The statements corresponding to various nodes are as under

Nodes	Statement No.
a	2-4
b	5
e	6-7
f	8
z	9-12
g	13-14
h	15
i	17
j	18
c	19
d	20

Step – 2: Calculation of Cyclomatic Complexity V(G) by three methods

Method – 1: V(G) = e – n + 2 ( Where “e” are  edges & “n” are nodes)

V(G) = 14– 11 + 2 = 3 + 2 = 5

Method – 2: V(G) = P + 1 (Where P – No. of predicate nodes with out degree = 2)

V(G) = 4 + 1 = 5   (Nodes b, f, g & c are predicate nodes with 2 outgoing edges)


Method – 3: V(G) = Number of enclosed regions + 1 = 4+1=3
( Here R1 – R₄ are enclosed regions and 1 corresponds to one outer region)

V(G) = 5 and is same by all the three methods.

Step – 3: Identification of the basis-set with five paths

Conclusions from the above tutorial:

Conclusion – 1: Each of these paths consists of at least one new edge. Hence this basis set of paths is NOT unique.

Conclusion – 2: Test cases should be designed for the independent path execution as identified above.

Conclusion – 3: We must execute these paths at least once in order to test the program thoroughly.

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