Unit testing is beneficial in determining whether subsets of an application are fit for use, and how automating that process makes it more efficient. Although unit testing can be implemented from first principles, the creation of a suitable environment to allow these isolated units to compile and run can be daunting. This example uses the IAR workbench and the LDRA tool suite to show how automated unit testing can be achieved for a single function, and how problem elements such as called functions and global variables can be handled efficiently. Such an approach is equally appropriate whether you are simply looking to improve code quality, or looking to comply with standards applicable to functional safety (IEC 61508, ISO 26262, IEC 62304, DO-178C...) or secure coding (SAE J3061, DO-326A, IEC 15408).