Testing multi-psi parsers

I need to make parser tests for multi-psi files. But it seems not working from the box. First I could reach with debugger, that FileViewProviderFactory is not working as intended. Is it possible? And if it is, how ?

I've dumbly copy-pasted from some sample project and thought that it init's all extensions i've implemented

CoreApplicationEnvironment.registerExtensionPointAndExtensions(new File("resources"), "plugin.xml", Extensions.getRootArea());

But it seems not enought for this. 

Upd: the problem been solve by overrding checkAllPsiRoots() method and make it returning false. In this case, test will check only base language parsing.