What is termed as replacing parts without proper diagnosis?

The term that describes replacing parts without proper diagnosis is referred to as "shotgunning." This approach involves making multiple changes or replacements in an attempt to fix a problem without systematically determining the root cause of the issue. Shotgunning can lead to unnecessary expenses and may not effectively resolve the underlying problem since it lacks a diagnostic foundation.

The other choices may contain aspects of the problem but do not capture the essence of replacing parts indiscriminately. Testing involves a systematic approach to evaluate the function and status of components before deciding on replacements. Speculation implies forming opinions or conclusions without firm evidence, which can lead to guesswork as well, but does not specifically denote the action of replacing parts. Guesswork, while similar, generally refers to making decisions based merely on assumptions rather than taking any concrete action like replacing parts. Hence, "shotgunning" is the most accurate term for this practice.