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

The rationale behind selecting the option that highlights both the lack of independence mitigated by independent testing and the idea that a better understanding of the code can lead to quicker defect detection is rooted in the principles of software testing and development practices.

When developers test their own code, their intimate knowledge of the codebase allows them to identify issues that may not be immediately evident to someone unfamiliar with it. This deep understanding helps them write targeted test cases that address specific functionalities, edge cases, or complex logic that might otherwise be overlooked. As a result, this can lead to quicker defect detection during the unit testing phase, which is crucial for maintaining quality and reducing downstream defects.

Moreover, the mention of the lack of independence raises an important consideration. While having developers test their own code presents certain challenges related to bias, the process can be complemented by independent testing efforts later in the development lifecycle, such as integration testing or system testing. These independent testing phases can help ensure that any potential biases or blind spots that developers might have during unit testing are addressed, thereby providing a more balanced testing strategy.

Other choices may refer to aspects that aren't as directly relevant to the fundamental practices of testing and may focus on points that distract from the essential reasons for developers to engage in unit testing.