Levels of Testing: Software Testing Hierarchy

The successful outcome of digital product creation is bug-free software that meets technical requirements and user needs. To confirm all these aspects, the application has to go through testing. But how do you approach it in a structured way? Where do you start, and what type of testing do you apply? To answer these questions, learn about levels of testing in software testing below.

Levels of Testing: What Is the Conception?

Software testing is a key process in software development based on specialists confirming the platform functionality, performance, reliability, and overall quality. While this is a fundamental procedure, a structured approach is needed. And this is where testing levels come into play.The conception of levels in software testing refers to a systematic view of the testing hierarchy. According to this approach, quality assurance (QA) teams break down the process into levels that go one by one in adherence to every stage of the software development lifecycle (SDLC). This methodology presents an organized way of testing a platform where all parts and aspects are checked, minimizing the appearance of errors in the future. So, let’s explore every testing level further below.

Unit Testing

QA specialists examine every unit or module separately from the whole system in unit testing. This procedure aims to ensure that every part of the platform works as intended before integration.

Testing modules in isolation is a beneficial practice in software testing. It helps to look at every detail precisely and discover all the issues at the early development stage. Thus, the errors are fixed, reducing the risk of subsequent defects.

Methods and Tools

Testers approach unit testing by applying these methods:

• Black-box testing. This method presents a possibility of testing the input-output behavior of the unit. It doesn’t consider internal code. Testers act from the users’ side and identify a unit working correctly if it provides the correct output.
• White-box testing. Opposite to black-box testing, in white-box testing, QA teams look at the unit performance “from within”. They analyze the code, paths, logic, and branches. It positively contributes to code quality and test coverage.
• Mock testing. Some units depend only on other elements, such as APIs or databases. In mock testing, specialists use simulated versions of the objects to reproduce the unit functionality.

Testers use such popular tools for conducting unit testing: JUnit for Java applications, NUnit for .NET, PyTest for Python, and Mocha for JavaScript.

Example

Imagine you are building a basic calculator application. You break down the whole system into units and test only one module: the ability to add numbers together. So, during testing, you check if the “add” button correctly adds two numbers, if it works the same with zero, and if it addresses negative calculations.

If all the cases show correct outcomes, you can be sure that the unit responsible for adding numbers works appropriately.

Integration Testing

When all units are tested separately, QA specialists proceed to the second level of software testing. In the integration testing, the aim is to check whether modules work properly together. Testers analyze data flows, interactions, and seamless communication between units. Integration testing targets different goals, such as detecting errors in data exchanges and dependencies, checking modules for their adherence to system requirements, and verifying communication protocols.

Types

There are several ways to execute integration testing. QA professionals can check module communication using these testing techniques:

• Big bang testing. This process refers to integrating all modules simultaneously and observing how they perform when working together. This approach is easy and quick to execute but can pose difficulties when identifying errors precisely.
• Incremental testing. When applying incremental testing, units are integrated one by one. There are also different ways of conducting it. Testers implement the high level during top-down testing and then proceed to the bottom. The opposite procedure is used in bottom-up testing: from lower-level units to high-level ones. When combining these two techniques, you will follow the hybrid or sandwich incremental testing.

Example

Let’s consider the example of the banking application. The task is to verify that two modules, login and user profile, communicate. The tracking process is as follows: the user logs in with unique credentials, the platform authenticates the user and sends a session token to the user profile, and the app shows correct data and history. By observing those two units working together, testers can identify if data transfer works appropriately by analyzing the results displayed on the user profile module.

System Testing

The third among the levels of testing, system examination checks the platform as a whole. It verifies the platform’s ability to work properly and according to the requirements. System testing aims to observe how the platform will act in an environment very similar to production. With the help of this process, testers verify whether the system works correctly as a unified organization and whether all its aspects, functional and non-functional, show high-quality performance.

Types

System testing can be conducted by using these approaches:

• Functional testing. During functional testing, QA specialists check if all the work functions are working properly. The goal is to spot if the platform handles inputs correctly from the beginning, usually a user log-in, to the end of the journey.

• Non-functional testing. This type of testing focuses on the system’s non-functional aspects. It checks the software’s ability to withstand heavy loads, deliver results quickly, and meet user expectations. After conducting non-functional testing, QA teams can report on the system’s reliability, stability, and overall performance.

Example

A perfect example of applying system testing can be a streaming platform welcoming thousands of users simultaneously. The testers’ task here will be to check functional and non-functional aspects, such as browsing films, playing videos, choosing subtitles, being compliant with all screen sizes, processing payments correctly, etc.

Acceptance Testing

The final validation step at the testing level is acceptance testing. It checks whether the finished product meets business and customer needs and is ready for deployment. Acceptance testing aims to show that the platform can work in a real environment. This procedure helps to verify that the project meets business requirements, that the users are content with the result, and that stakeholders approve the outcome.

Types

Acceptance testing can also be conducted using different approaches, such as:

• Alpha testing. During alpha testing, testers, other internal teams, and stakeholders gather to check software performance in a controlled environment. It helps to locate the issues before the product launch.

• Beta testing. This type of software testing has a group of real users who are ready to check it for functionality, usability, and overall quality. Beta testing results also confirm that the app satisfies end customer needs.

Example

Let’s take an e-commerce website as an example and apply beta testing. The flow will be the following: a focused group of end users will use the platform’s features. They will start by choosing products, adding them to the cart, processing payment, adding any upsells, and getting a purchase confirmation.

The feedback gained from this experiment can uncover bugs and also point out user experience issues.

Conclusion

Software testing is a comprehensive procedure that is easier to execute by breaking it down into levels. Those stages follow the development route, from isolated unit testing to user adoption testing. To follow a correct hierarchy of testing, it is crucial to build a testing strategy and include all testing levels there. Clear objectives, goals, tools, and wireframes will help you create a coherent process and fix all issues early so that end customers receive an excellent application!