Consider the following simplified example (not a code which can be compiled). When running the TestA.test(), A.x() will call a real A.y() and not the mocked one. Is there any way to do that?

the class which should be tested:

public class A {
  public void x() {
    Object obj = y();
  }

  public Object y() {
    return result;
  }
}

the testing class:

public class testA {
  @Test
  void test() {
    A a = spy(A.class);
    when(a.y()).thenReturn("mocked");
    a.x();
  }
}