Cyclomatic Complexity

Cyclomatic complexity of a code section is the quantitative measure of the number of linearly independent paths in it. It is a software metric used to indicate the complexity of a program. It is computed using the Control Flow Graph of the program. The nodes in the graph indicate the smallest group of commands of a program, and a directed edge in it connects the two nodes i.e. if second command might immediately follow the first command. 

For example, if source code contains no control flow statement then its cyclomatic complexity will be 1 and source code contains a single path in it. Similarly, if the source code contains one if condition then cyclomatic complexity will be 2 because there will be two paths one for true and the other for false. 

Mathematically, for a structured program, the directed graph inside control flow is the edge joining two basic blocks of the program as control may pass from first to second. 
So, cyclomatic complexity M would be defined as, 


M = E – N + 2P 

E = the number of edges in the control flow graph 
N = the number of nodes in the control flow graph 
P = the number of connected components 

Steps that should be followed in calculating cyclomatic complexity and test cases design are: 

Let a section of code as such: 

A = 10
   IF B > C THEN
      A = B
      A = C
Print A
Print B
Print C


Control Flow Graph of above code


The cyclomatic complexity calculated for above code will be from control flow graph. The graph shows seven shapes(nodes), seven lines(edges), hence cyclomatic complexity is 7-7+2 = 2. 

Use of Cyclomatic Complexity: 

Advantages of Cyclomatic Complexity:.

Disadvantages of Cyclomatic Complexity:


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