Testing IDEA plugins with multiple modules


For the tests of the Osmorc plugin, I often need a setup with more than one module. Unfortunately IdeaProjectTestFixture comes only with one module and it's not easy to create more module in it. So I normally create module in a testdata folder and load them manually via ModifiableModuleModel.lloadModule.
Unfortunately this only creates a module and no settings are read from the module file. I also have to manually add the content roots, facets and dependencies on other modules. That's a bit tedious. What do I need to execute to make IDEA read the rest of the module file?