module dependency problems

I am developing app using IDE 8.1.
I have three modules in my app module A,B and C.
modules C is utility module so module A and B depend on C.
module A is top level, so have dependency of B and C.
When module A use class in module B,  java.lang.NoClassDefFoundError is found about class in module C.

Of cause, Packages in module B and C are exported as public.

When I am doing unit test, this error is not found.
The error is found when I run in IDE.
Am I wrong? or Is there any solution?
Thanks!!