Structural Testing : Introduction

• The structure of a software product is responsible for designing test cases in order to test a software product.Since, the whole structure is known as structural testing, it is also known as white box testing.
• Structural testing is more technical than functional testing as it attempts to design test cases from the source code and not from the specifications.
• The major structural testing approaches are:
  1. Statement Coverage: In this, the aim is to achieve 100% statement coverage i.e. each and every statement of program is executed.
  2. Branch Coverage: In this, the aim is to achieve 100% branch coverage i.e. every branch either containing “true” or “false” conditions needs to be executed.
  3. Path Coverage: This technique corresponds to test all possible paths i.e. it is a combination of branch and statement coverage techniques. 

Structural Testing : Types

• Structural testing can broadly be classified into four types. These are:

Structural Testing : Types

1. Control Flow testing
   • In this, various paths of programs and  various test cases are designed to execute those paths which ultimately results in finding out the cyclomatic complexity of the programs.
2. Data Flow Testing
   • It is a technique used for determining improper use of data inside a software programs.
   • Incorrect variable declaration, Multiple times declaration and assigning values to variables can be some of the examples.
3. Slice Based Testing
   • Slicing a software program and testing those slices individually for defects and errors.
4. Mutation Testing
   • When small changes are made in some certain statements of source code to check whether the test cases are able to find the errors or not.
   • These changes are known as mutants.
   • The changes are very small such that they does not affect the overall objective of the program.
   • The goal of mutation testing is to assess the quality of test cases which should be powerful enough to fail the mutants in the code.

Structural Testing : Cyclomatic Complexity

• The concept of cyclomatic complexity is used to find the number of independent paths present in a program graph.
• There are three methods to calculate cyclomatic complexity. These are

If,

V(g) = Cyclomatic complexity.

n = Number of nodes.

e = Number of edges.

then,

1. V(g) = e-n+2

2. V(g) = Number of regions in the program graph.

3. V(g) = Number of predicate node + 1.

where, predicate node is the node with 2 outgoing edges.