Levels of Software Testing

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Introduction to Levels of Software Testing

Software testing is a process of testing of software or product to ensure that the software or product is bug-free. Levels of software testing are process in which every component or small unit of software is tested. There are different levels of software testing; each has its features, advantages, and disadvantages. These different levels of software testing are designed to test the software performance and behaviors of the software at different stages.

There are different stages in the software development lifecycle like requirements, design, coding development, and execution. Levels of software testing are used to find those missing areas between these stages of the software development lifecycle.

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There are four different levels of software testing, which are as follows:
1. Unit testing
2. Integration testing
3. System testing
4. Acceptance testing

Let us discuss those different levels one by one in detail.

1. Unit Testing

Unit testing is also known as the first level of testing. A unit means a small component. Unit testing is the process of testing small components of software or product. This testing is performed using the white box testing method. One of the main advantages of unit testing is it allows each small component of the software to be tested separately. The developers perform this testing. This testing aims to test each component of the software to check that it is functioning well or not, does it works as it is intended, does it fulfills the specified requirements.

Advantages of Unit Testing

As unit testing tests only components of the software, it is easy to debug the software. If some error occurs, only the latest changes that are made need to be tested.
Unit testing saves time as well as cost. The cost of solving defects is less as compared with others.
In unit testing, the development process is faster because it requires fewer efforts to find and fix bugs than another type of testing.
Codes can be reused in unit testing.

The steps involved in Unit Testing are as follows.

Unit Test Plan: This process involves preparing test plans, reviewing them And cross-checking the requirements.
Unit Test Cases: This process involves test cases for various scenarios with combinations of input and output.
Unit Testing: This is the last step where all planned tests are executed one by one.

2. Integration Testing

This is the second level of software testing, where each component or unit is combined and tested as a whole. The goal behind this testing is to ensure that software or product is working properly when the unit of software is combined together with other components. As its name suggests, it is used to identify errors between interacted components. For integrating testing, any of the black box testing, white box testing, grey box testing can be used. This testing is performed after the unit testing but before the system testing.

Approaches for Integration Testing

Big bang Approach: In a big bang approach, all units are combined together as a whole and tested at one go.
Top-down Approach: In the top-down approach, units at the top level are tested first, and then units at low levels are tested one by one.
Bottom-up Approach: In a bottom-up approach, units at a low level are tested first, and then units at a high level are tested one by one. This approach is the reverse of the top-down approach.
Sandwich or hybrid Approach: This approach is a combination of a top-down approach and a bottom-up approach.

3. System Testing

System testing is the third level of software testing. In system testing, the complete system or software is tested in various environments. This testing aims to test the whole system in a different environment and ensure that they meet the specified requirements.

Integration testing commonly uses a black box testing method. This testing is performed after the integration testing and before the acceptance testing. This testing is carried out by individual testers who are independent of the developers’ team. Its main aim is to test the functionality of the system against its specified requirements.

The steps involved in System Testing are as follows.

System Test Plan: This process involves preparing test plans, reviewing them And cross-checking the requirements.
System Test Cases: This process involves test cases for various scenarios with combinations of input and output.
System Testing: This is the last step where all planned tests are executed one by one.

4. Acceptance Testing

Acceptance testing is the last level of software testing. In this testing, software or product is tested to check the acceptability. It checks the compatibility of the system against the specified requirements. It also checks whether it is ready for delivery or not. To perform Acceptance testing, the black box testing method is used.

Types of Acceptance Testing

Alpha Testing

Alpha testing is performed by the people who are members of the Organization and not involved in the development team. It is also called as internal acceptance testing as it tests by its own members.

Beta Testing

Beta testing is performed by users who are going to use those in the future. It is also called as external acceptance testing as the outsider user tests it.