Christianity is heading for a full allegorization

[Spongebob]

No, you have two hypotheses:
1. that ice cream trucks cause drownings
2. that both ice cream trucks and drownings are 'caused by' summer.

The trick is to find situations where those two hypotheses give different predictions and then test those situations. That is exactly what was proposed.

Don't forget about the null hypothesis, that this idea is all wrong and something else altogether causes drownings, like Pokémon Go.