What are valid justifications for developers testing their own code during unit testing?

The justification for developers testing their own code during unit testing is well-supported by the notion that their familiarity with the code can significantly enhance defect detection efficiency. Developers possess intricate knowledge of the code they have written, including its structure, logic, and potential pitfalls. This insight allows them to identify bugs and logical errors more effectively during unit testing compared to someone less acquainted with the code.

Additionally, while independence in testing is ideal, it is often complemented by further independent verification in later testing phases, such as integration and system testing. Therefore, the potential lack of independence at the unit testing stage can still lead to productive outcomes when balanced with these subsequent independent evaluations.

Furthermore, the premise that having a better understanding of the code enables quicker defect detection is key. This capability typically results in a more thorough and informed testing process. This understanding helps in designing relevant test cases that might spot issues both earlier and more efficiently than external testers could achieve.

This perspective acknowledges that a collaborative approach—where developers and testers contribute their expertise at different stages—enriches the overall quality assurance process, ultimately leading to a more robust software product.