No this is incorrect you can inline ruby in HAML as effectively as writing it normally.
Please check out on of my partials here:
In the case of testing the Helper in a partial I would not create the method name or enclosing block - focus on the code that does stuff.
In my partial you can see that its all inline - others would put this in a gem, but I like the fact that the code is in a modular place that I can directly edit and see the effects.
So in most cases I go for partials over helpers.