**Basis path testing** is a type of white-box testing that tests all possible independent paths in the control flow graph of a program.

>Note:
> * A **path** is the route of nodes in the control flow graph that a program takes from one point to another.
> * An **independent path** is a path that adds at least one node in the already defined independent paths. In other words, the independent paths of a program are all unique.
# Steps for basis path testing
To conduct *basis path testing* of a program, follow the steps below:
1. Draw the control flow graph of the program.
2. Calculate the **cyclomatic complexity** of the control flow graph. This will be the maximum number of independent paths in the graph.
3. Identify independent paths in the control flow graph.
4. Design test cases based on the independent paths identified so that the test cases execute all independent paths.

# Advantages of basis path testing
The advantages of conducting *basis path testing* are:
* Basis path testing reduces the number of redundant tests.
* All program statements are executed and tested at least once.
* It guarantees complete branch coverage.

# Example 
Consider the code snippet below, for which we will conduct basis path testing:

int num1 = 6;
int num2 = 9;
if(num2 == 0){
  cout<<"num1/num2 is undefined"<<endl;
}else{
  if(num1 > num2){
    cout<<"num1 is greater"<<endl;
  }else{
    cout<<"num2 is greater"<<endl;
  }
}

## Step 1: Draw the control flow graph
The control flow graph of the code above will be as follows:

## Step 2: Calculate cyclomatic complexity
The cyclomatic complexity of the control flow graph above will be:


where,
* `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 in the control flow graph.

## Step 3: Identify independent paths
The independent paths in the control flow graph are as follows:
* *Path 1*: 1A-2B-3C-4D-5F-9
* *Path 2*: 1A-2B-3C-4E-6G-7I-9
* *Path 3*: 1A-2B-3C-4E-6H-8J-9

## Step 4: Design test cases
The test cases to execute all paths above will be as follows:


Path	Input values
Path 1: 1A-2B-3C-4D-5F-9	num1 = 9 num2 = 0
Path 2: 1A-2B-3C-4E-6G-7I-9	num1 = 4 num2 = 2
Path 3: 1A-2B-3C-4E-6H-8J-9	num1 = 6 num2 = 8

What is basis path testing?

Steps for basis path testing

Advantages of basis path testing

Example

Step 1: Draw the control flow graph

Step 2: Calculate cyclomatic complexity

Step 3: Identify independent paths

Step 4: Design test cases