### Question:
CustomerCore extends Customer { @Override public boolean addRole(Role role) { return role .instance() .map(inst -> { roles.put(role, inst); return true; }) .orElse(false); } CustomerCore(); @Override boolean addRole(Role role); @Override boolean hasRole(Role role); @Override boolean remRole(Role role); @Override Optional<T> getRole(Role role, Class<T> expectedRole); @Override String toString();  }### Answer:
@Test public void addRole() { var core = new CustomerCore(); assertTrue(core.addRole(Role.Borrower)); }