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Low-level testing is a kind of software testing, that is checking if each module, function, class, and method work correctly. It verifies the system functionality at the source code level, processor instructions, registers, memory, or hardware interface. Low-level tests are commonly used in embedded systems that are integrated with hardware and have limited resources.

The aim is to identify and eliminate logical, syntactical, or implementation bugs in the code before it’s integrated with other system components. Typically, low-level tests are carried out by developers creating and modifying the source code.

This kind of testing is necessary to maintain the quality and reliability of our software, but it requires a creative approach due to many challenges, such as:

• Changing requirements: In an agile approach, the requirements are often changing and incomplete, which makes it difficult to write low-level tests in the early project phase. Low-level tests need to be flexible and easily adaptable to source code changes.
• Code complexity: Source code can be complicated and difficult to understand, especially if it’s written in low-level languages such as Assembler or C. The code can also contain numerous dependencies, conditions, loops, exceptions, or recursions, making analysis and testing challenging.
• Integration with other modules: Only the functionality of single code units is being checked by low-level testing, not guaranteeing they will work correctly with other modules or services used by the application.
• Lack of documentation: The source code can be insufficient or not documented at all, which makes checking and understanding difficult. The documentation may also be outdated or inconsistent with the code itself, leading to bugs and inaccuracies.
• Time shortage: Low-level testing may be time-consuming and laborious, especially if the code is extensive, and often changed.  Developers may be put under pressure by deadlines and priorities and not have enough time to test the code systematically and thoroughly.
• Equipment shortage: This kind of testing requires specialized equipment such as debuggers, compilers, linkers, emulators, simulators, or code analyzers. These kinds of tools can be unavailable, expensive, difficult to use, or incompatible with the code or testing environment.
• Communication:  Both the tester and developer can have different perspectives on what is important and what the customer’s expectations are. They can also have different work approaches, which might influence cooperation and information exchange. A significant issue that can arise is the various levels of knowledge and experience between testers and developers, which can affect their trust and respect toward each other.

Faced with that kind of problems, our testers seek solutions that will make low-level testing easier, and increase its efficiency and quality.

Some of the possible solutions:

• Test planning: involves defining the objectives, scope, strategy, methodology, and success criteria for the tests. Test planning should be based on an analysis of requirements, risks, and project limits. It is crucial to ensure the consistency, effectiveness, and completeness of the test process.
• Using testing frameworks: Testing frameworks are sets of tools and libraries that support the software testing process. They can automate the creation and execution of low-level tests, generate statistics and reports, and manage data testing and defects.  Using testing frameworks can significantly increase the productivity and quality of low-level testing.
• Using test-driven development (TDD) and behavior-driven development (BDD) techniques: TDD and BDD are programming methods that involve writing tests before or along with the code. They require developers to define expected behavior and test results in the form of tests, and to write code to meet those tests. TDD and BDD can improve the quality of code and tests because they enforce clear specifications and verification requirements.
• Using refactoring techniques and code review: Refactoring is a process of improving the structure and quality of code without changing its functionality. Code review is a process of checking for bugs, inconsistencies, and potential improvements by other developers. Using refactoring techniques and code reviews may help detect and eliminate bugs, increasing the code readability and simplicity, making it easy to maintain.
• Using code coverage techniques and mutation techniques: Code coverage is a measure that shows, in percent, how much code has been executed during the test process. Mutation testing is a technique that involves introducing random changes to the code and reviewing whether the tests can detect them. Using coverage code techniques and mutation testing can help evaluate the effectiveness and completeness of low-level tests.

I’d like to emphasize that low-level testing, although challenging, is also a great opportunity for learning and professional growth in the field of software development. It provides an opportunity to learn about the structure and functionality of the software, which is crucial for ensuring its quality and reliability. Low-level testing requires continuous improvement of technical and analytical skills, enabling testers to enhance their qualifications and adapt to constantly changing market demands.

Therefore, it provides testers with opportunities to make a career in the IT market and expand their scope of competence and specialization.

Author:
Karol Witkowski
Software and Hardware Testing Team

Check out our previous article, describing the fundamental steps of designing an effective test environment for embedded systems.