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What is branch testing?

Kainat Asif

Branch testing is a type of white-box testing that is used to test every possible branch in the control flow graph of a program. In branch testing, every branch in the code is executed at least once.

Why do we need branch testing?

We need branch testing because:

  • It ensures that no branch in the code leads to abnormal behavior.
  • It guarantees that all branches in the code are reached.
  • It is a quantitative measure of the code coverage of the program.

How to calculate branch testing

Branch testing of a program is carried out by calculating a metric called branch coverage. Branch coverage is the ratio of the number of branches covered to the total number of branches. Branch coverage can be calculated as:

Example

Consider the code snippet below, which is a simple program to find the maximum of two numbers:

int a = 2;
int b = 5;
if(a>b){
  cout<<"a is max";
}else{
  cout<<"b is max";
}

Control flow graph

The control flow graph of the code above will be as follows:

Branch testing

Branches

The branches in the control flow graph above are A, B, C, D, E, F, and G.

Branch Coverage

For maximum branch coverage, we take the path:

Path1 = 1A-2B-3C-4D-5F-7

  • Covered branches = A, B, C, D, F
  • Uncovered branches = E, G

The branch coverage of path1 will be:

Branch coverage = (number of branches covered / total number of branches) x 100

Branch coverage = (5 / 7) x 100

Branch coverage = 71%

Branches E and G are not covered in path1. To cover branches E and G, we take the path:

Path2 = 1A-2B-3C-4E-6G-7

  • Covered branches = A, B, C, E, G
  • Uncovered branches = D, F

The branch coverage of path2 will be:

Branch coverage = (number of branches covered / total number of branches) x 100

Branch coverage = (5 / 7) x 100

Branch coverage = 71%

For 100% branch coverage, we combine both paths, path1 and path2. The final branch testing of the control flow graph above becomes:

  • Path1 = 1A-2B-3C-4D-5F-7
  • Path2 = 1A-2B-3C-4E-6G-7

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Kainat Asif
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