Types of Functional Testing

1. Unit Testing
2. Integration Testing
3. System Testing

1. Unit Testing

Unit testing is a method of testing individual units or components of a software application. It is typically done by developers and is used to ensure that the individual units of the software are working as intended. Unit tests are usually automated and are designed to test specific parts of the code, such as a particular function or method. Unit testing is done at the lowest level of the software development process, where individual units of code are tested in isolation.

Advantages of Unit Testing:

Some of the advantages of Unit Testing are listed below.

• It helps to identify bugs early in the development process before they become more difficult and expensive to fix.
• It helps to ensure that changes to the code do not introduce new bugs.
• It makes the code more modular and easier to understand and maintain.
• It helps to improve the overall quality and reliability of the software.

Note: Some popular frameworks and tools that are used for unit testing include JUnit, NUnit, and xUnit.

• It’s important to keep in mind that Unit Testing is only one aspect of software testing and it should be used in combination with other types of testing such as integration testing, functional testing, and acceptance testing to ensure that the software meets the needs of its users.
• It focuses on the smallest unit of software design. In this, we test an individual unit or group of interrelated units. It is often done by the programmer by using sample input and observing its corresponding outputs. 

Example:

1. In a program we are checking if the loop, method, or function is working fine.
2. Misunderstood or incorrect, arithmetic precedence.
3. Incorrect initialization.

2. Integration Testing

Integration testing is a method of testing how different units or components of a software application interact with each other. It is used to identify and resolve any issues that may arise when different units of the software are combined. Integration testing is typically done after unit testing and before functional testing and is used to verify that the different units of the software work together as intended.

Different Ways of Performing Integration Testing:

Different ways of Integration Testing are discussed below.

• Top-down integration testing: It starts with the highest-level modules and differentiates them from lower-level modules.
• Bottom-up integration testing: It starts with the lowest-level modules and integrates them with higher-level modules.
• Big-Bang integration testing: It combines all the modules and integrates them all at once.
• Incremental integration testing: It integrates the modules in small groups, testing each group as it is added.

Advantages of Integrating Testing

• It helps to identify and resolve issues that may arise when different units of the software are combined.
• It helps to ensure that the different units of the software work together as intended.
• It helps to improve the overall reliability and stability of the software.
• It’s important to keep in mind that Integration testing is essential for complex systems where different components are integrated.
• As with unit testing, integration testing is only one aspect of software testing and it should be used in combination with other types of testing such as unit testing, functional testing, and acceptance testing to ensure that the software meets the needs of its users.

The objective is to take unit-tested components and build a program structure that has been dictated by design. Integration testing is testing in which a group of components is combined to produce output. 

Integration testing is of four types: (i) Top-down (ii) Bottom-up (iii) Sandwich (iv) Big-Bang

Example:

1. Black Box testing: It is used for validation. In this, we ignore internal working mechanisms and focus on “what is the output?”
2. White box testing: It is used for verification. In this, we focus on internal mechanisms i.e. how the output is achieved.

3. System Testing

System testing is a type of software testing that evaluates the overall functionality and performance of a complete and fully integrated software solution. It tests if the system meets the specified requirements and if it is suitable for delivery to the end-users. This type of testing is performed after the integration testing and before the acceptance testing.

System Testing is a type of software testing that is performed on a completely integrated system to evaluate the compliance of the system with the corresponding requirements. In system testing, integration testing passed components are taken as input. The goal of integration testing is to detect any irregularity between the units that are integrated. 

Advantages of System Testing:

• The testers do not require more knowledge of programming to carry out this testing.
• It will test the entire product or software so that we will easily detect the errors or defects that cannot be identified during the unit testing and integration testing.
• The testing environment is similar to that of the real-time production or business environment.
• It checks the entire functionality of the system with different test scripts and also it covers the technical and business requirements of clients.
• After this testing, the product will almost cover all the possible bugs or errors and hence the development team will confidently go ahead with acceptance testing.

Welcome to the world of software testing, which ensures the quality and reliability of software applications. Understanding the various types of software testing is essential for developers and quality assurance professionals alike.

In this guide, we’ll explore the fundamental categories of software testing, from unit testing to security testing, helping you navigate and ensuring your software will meet the highest standards of performance and functionality.