Developer testing is crucial to quality code produced in a timely fashion. The answer is, of course, no. Testing doesn't achieve quality, it assesses whether a certain quality level has been achieved . This assessment, of course, can be used by all involved to guide further development efforts, and thus, as information, it is a good for quality, but testing on its own doesn't achieve anything. It depends on the project, of course.
Some projects are simple enough that it is practical to apply black box testing alone.
In most projects, though, it is entirely impractical. There is a geometrical theorem which says that anything which can be constructed with a straight edge and compass can also be done with a compass alone. Even if the compass alone is sufficient, the task is much easier when you allow the use of the straight edge. The ugly truth is that testing, particularly black box testing, is usually the easiest tool to use, politically . Other tools affect the way that development does its work, and this intrusion is often difficult to sustain unless the entire organization understands and supports the use of the tools.