unit testing - mock a public method of other class in a method (java) -

i new mockito. code:

public class a{    public a{       ...       b.fff();  //the function want mock       ...    } }  public class b{     public boolean fff(){        ...        ...  //connect db        ...      } } 

for unit test,

public class atest{      @test     public void test(){         mock_a = new a();         assert.assertnotnull(mock_a);     } } 

because of function "b.fff()" need connect db,so mock function "b.fff()" return true or false let test can work without environment.

i tried code like：

public class atest{      @test     public void test(){         powermockito.when(b.fff()).thenreturn(true);         assert.assertnotnull(new a());     } } 

but isn't working.

is there solution using mockito(or powermock)?

thanks.

what want here inject mock of b a. long term require setting inversion of control container, if simple test app can start (pseudo code here ... i'm typing on phone):

public class a{   public a(b binstance){     this.b = binstance;   }   public void foo() {     b.dosomethingwithdb();   } } 

in test, mock b , set expected return value, inject constructor of a.

do reading on ioc - make testing easier , make better programmer in long run.