Which step contributes to avoiding light failure during a dive?

Testing lights before entering the water is crucial for ensuring that your equipment is functioning properly before a dive. By conducting a thorough check of your light sources, you can verify that they are charged, operational, and free of any damage or malfunctions. This proactive measure significantly reduces the risk of encountering a light failure when submerged, which can be particularly critical in cavern diving scenarios where visibility may be limited and a reliable light source is essential for navigation and safety.

The other options, while they may have their own merits, do not directly address the importance of verifying equipment functionality before the dive, which is vital for avoiding unexpected issues during underwater exploration.