In this, we will drive test cases using Data flow testing approach by considering the Quadratic equation example. The first step is to create a flow graph from the code of the Quadratic Equation.

Using the flow graph, create a Decision to Decision Graph ( DD Graph) by converting each set of consecutive nodes into a single node.

Replace these numbers with correspondent DD nodes.

Create a Defined and Used node table to get a clear view of variable usage.

On the basis of the above table, we will generate du and dc path respectively.

All the ‘Y’ in the above table are DC path and ‘Path nodes’ are DU paths.

Now, create the test cases from input provided by the user in such a way that all the paths get covered.

A quadratic equation is a polynomial equation, having highest degree of two. The equation is represented in the form of ax²+bx+c where a can’t be 0, c is constant, a and b are coefficients. There can be two answers of x which is termed as roots.

This Quadratic formula is applied only when b2– 4ac >= 0.
such that,
If b²– 4ac > 0 , means the eqn. has more than one real roots
if b²– 4ac = 0 , represent equal or single root
if b²– 4ac <0, represents imaginary root
Lastly, if a is 0, then the equation would not be considered as a quadratic equation.

A quadratic equation is an equation having a degree of 2.  There are 4 possibilities, these are real roots, equal roots, imaginary roots and not a quadratic equation.

Steps to calculate quadratic equation

• Read a, b, c values
• if a == 0, then it’s not a quadratic equation
• else,
  calculate result = b² – 4ac
  • if result > 0 then
    compute the real roots using the formula
    print root1,root2 values
  • Else if result = 0 then
    compute the equal roots using the formula
    print root1,root2 values
  • Else if result < 0 then
    roots are imaginary
    print no solution

C Program for Quadratic Equation

Program:

#include<conio.h>
#include<stdio.h>
#include<math.h>
void main (){
  float a, b, c, result;
  printf (" ax^2 + bx + c, \n enter the values of a, b and c : = ");
  scanf ("%f %f %f", &a, &b, &c);

  result = (b * b) - (4 * a * c);
  if (a == 0)
    printf ("The equation is not a quadratic equation");
  else if (result > 0)
    {
      result = sqrt (result);
      printf ("Real roots are, %f,%f \n", (-b - result) / (2 * a),
        (-b + result) / (2 * a));
    }
  else if (result == 0)
    {
      result = sqrt (result);
      printf ("equal root, %f,%f \n", (-b) / (2 * a), (-b) / (2 * a));
    }
  else
    {
      printf ("Root are imaginary ;\n No Solution");
    }

  getch ();
}

Output:

Imaginary Roots or No solution

ax^2 + bx + c, 
 enter the values of a, b and c : = 11 5 5
Root are imaginary ;
 No Solution

Real roots:

 ax^2 + bx + c, 
 enter the values of a, b and c : = 5 5 1
Real roots are, -0.723607,-0.276393 

Equal roots:

 ax^2 + bx + c, 
 enter the values of a, b and c : = 5 10 5
equal root, -1.000000,-1.000000 

Not Quadratic

 ax^2 + bx + c, 
 enter the values of a, b and c : = 0 5 5 
The equation is not a quadratic equation