Under which condition is a spring switch not required to be tested?

A spring switch is not required to be tested when it is spiked. Spiking a switch indicates that it has been secured in a position and will not operate or move, thus negating the need for testing the switch's operational functionality. The main purpose of testing a spring switch is to ensure it can function properly when required, especially in situations where trains may need to use it. When a switch is spiked, it's effectively locked in place, which means that it does not pose any risk of malfunction while trains are operating.

In contrast, other options address conditions where the functionality of the switch might still be relevant. For example, if the switch indicator displays caution, it suggests there may be an issue that warrants testing. Similarly, the proximity of trains or recent inspections does not eliminate the necessity for testing if there's any uncertainty about the switch's operational status. These scenarios still require awareness and potential verification to ensure safety and functionality in train operations.