Mocking an Object's method calls by EasyMock after injecting it using PowerMock

I have a following class in my project for which I am trying to write a test case

Class A{
    a(){
        B b = new B();
        int ans = b.somefunction();
    }
}

I need to mock somefunction() call in above class for my test

I tried following to achieve this

@RunWith(PowerMockRunner.class)
@PrepareForTest({A.class,B.class})
Class TestA{
    testa(){
        EasyMock mb = EasyMock.createMock(B.class);
        PowerMock.createMock(B.class);
        PowerMock.expectNew(B.class).andReturn(mb);
        EasyMock.expect(mb.somefunction()).andReturn(0);
        EasyMock.replay(mb);
        PowerMock.replay(B.class);
    }
}

but it always gives Java.lang.AssertionError: Unexpected method call B.somefunction()

I have PowerMock 1.5.5 and EasyMock 3.2 in my package

Can someone help me with the above problem and help me figure out where exactly I am going wrong. I am new to using EasyMock and PowerMock.

Does there exist a simpler way to test given class.