For a situation where you have multiple months would you go and write another feature spec? A full feature spec feels a little heavy weight for the difference between the existing spec. Would that be a situation where you would pull the logic out into a helper and then test the functionality in an isolated unit there. I suppose another alternative would be to simply trust the pluralize implementation but that doesn’t protect you against removing the pluralize call later if you did refactoring to the view.
I guess the more general question here is, how granular should you make the integration tests. One one had they are slow so having less of them is better but on the other hand you want to get some confidence that certain permutations for the view are tested and protected against change.