Structural Testing

Making sure that code is reliable and high quality is essential in the rapidly changing software development field. Structural testing plays an important role in achieving this by focusing on the inner workings of applications.

What is Structural Testing?

Structural testing is an approach that finds out what is happening inside an application. This method helps software developers and testers understand the software’s internal behavior; since the internal behavior is known to the users, this is called white box testing or glass box testing.

Understanding Structural Testing

Imagine you are a developer writing a function to identify whether a given number is odd or even.

You can create test cases that cover a variety of scenarios, such as passing even and odd numbers, in addition to edge cases like zero and negative values. By implementing this, you can ensure that your function appropriately handles all potential inputs by testing each conditional branch.

Structural Testing vs Functional Testing

Before comparing structural testing with functional testing, you need to know what functional testing is, so here is a definition:

“Functional testing is a method to check whether an application satisfies all the functional requirements and specifications.”

How do we check whether the functional requirements are implemented?

By checking the output or response of the application. That means we are not evaluating the code, so functional testing is called black box testing.

As mentioned earlier, structural testing should be performed by a developer, but functional testing can also be performed by a quality assurance engineer, who only executes tests from a black box perspective.

Structural testing tools use data analysis methods to improve an application’s internal structure; on the other hand, functional testing tools work on event analysis methodology to prevent business loss.

Types of Structural Testing

Did you know that structural testing is divided into four subcategories?

Structural testing can be divided into four types:

Mutation Testing
Data Flow Testing
Control Flow Testing
Slice-based Testing

Let’s examine each one in detail.

Mutation Testing

The purpose of a mutation test is for developers to intentionally introduce an error into an application to see if the test cases can recognize the error.

Mutation tests can be divided into three types. Let’s discuss these types with simple code snippets.

Value Mutation: As the name implies, value mutation testing purposefully introduces minor modifications (mutations) to the program’s values or parameters to assess the efficacy of test cases.

// The original code
let valueA = 295;
let valueB = 105;
let output = (valueA + valueB) / 5;

console.log('Output : ', output);

Let’s apply value mutation to the given code snippet.

// Mutated code
let valueA = 695; // value mutation
let valueB = 105;
let output = (valueA + valueB) / 5;

console.log('Output : ', output);

In this example, we have applied the value mutation by mutating the constant value, but you can also mutate the function parameters.

Decision Mutation: Decision mutation is a method of finding errors by changing the logical or arithmetic operators. Here’s an example code snippet.

// Original Code
if (valueA > valueB) {
console.log('Large');
} else {
console.log('Small');
}

Let’s apply decision mutation to the given code snippet.

// modified Code
if (valueA < valueB) { // decision mutation
console.log('Large');
} else {
console.log('Small');
}

Statement mutation: A statement mutation is a method of finding errors by altering or removing a statement(s).

// Original Statement
let valueC = valueA - valueB;

// Statement mutation
let valueC = (valueA + valueB) - 20;

Data Flow Testing

By performing data flow testing, developers can ensure that every definition of a variable is tested for the paths on which it is used.

Data flow testing can be used to find errors, such as variables that are declared but are never used, as well as variable usage before declaration.

For a clear understanding, let’s examine a code example.

function checkPositive(number){
  let result;

  if (number > 0) {
    result = 'Positive number';
  } else {
    result = 'Negative number';
  }
  return result;
}

// calling the function
console.log(checkPositive(8));

By replacing the 8 with a negative value(e.g., -6), we can verify that the variable result is properly tested in all execution paths.

Control Flow Testing

Control flow testing is a type of structural testing that focuses primarily on a program’s control flows. It describes the sequence of execution of a code segment.

The purpose of control flow testing is to determine whether all paths through the program’s control flow are tested, including each decision point and branch. Control flow testing can detect common infinite loops and logic errors.

Slice-Based Testing

A slice is a set of statements that directly or indirectly affects the values at a particular point of interest. Testing a slice of a program is known as slice-based testing.

Since the complex logic is cut down into small independent slices, it can be easy to understand the code that belongs to a specific feature.

Structural Testing Tools

While many tools for structural testing are available, here are a few that software development companies frequently utilize.

qodo

qodo is one of the best tools for structural testing. It uses Artificial Intelligence (AI) to automatically produce unit tests and enhance existing tests.

qodo supports many programming languages, including Python, JavaScript, TypeScript, Go, and Java. Developers and software testers can use the qodo in three different ways.

Plugin for an IDE: Qodo Gen
Plugin for Git: Qodo Merge
CLI tool: Qodo Cover

JUnit

JUnit is a popular open-source testing framework for Java applications. It allows developers to create and execute repeated tests that guarantee the accuracy and reliability of their code, and developers can achieve high code coverage by creating JUnit tests for error situations and edge cases.

Cucumber

Cucumber is another popular open-source testing tool that facilitates behavior-driven development.

A human-readable language allows testers to develop tests that minimize the gap between technical and non-technical stakeholders.

Although it can be used with other programming languages, such as Java, Ruby, and JavaScript, Cucumber is flexible and can be integrated into multiple technology stacks.