What are the ways in which the universal, inclusive conception of French nationalism was tested by a (racially-conceived) particularistic, exclusive one?
I'm at loss, I don't know what's being asked. What does this mean?
This asks in which way (or ways) one side of a thing was tested by another one (another side).
The sides of the thing are:
The thing tested is nationalism.
In which way side a) tested side b)?
note: I don't know if my interpretation of sides is correct, but that should not matter for understanding the structure of the question.
The distinction is between those who think that being French is wonderful and that everybody should want to be French, and those who think that being French is wonderful partly because certain people are not (for example immigrants from north and sub-Saharan Africa) and that such people should not be allowed to become French even if they want to.
I believe they are asking how people perceive French Nationalism from the viewpoint of both the supporter (of Nationalism) and from the view of a separate social group (in this case racial group).