@Test
 public void assignCausesAssignmentOfTheIntervalsRegisterToTheGivenRegister() {
   Register r = new Register(0);
   CompoundInterval ci = new CompoundInterval(DEFAULT_BEGIN, DEFAULT_END, r);
   Register s = new Register(1);
   RegisterAllocatorState regAllocState = new RegisterAllocatorState(0);
   assertThat(ci.isAssigned(regAllocState), is(false));
   assertNull(ci.getAssignment(regAllocState));
   ci.assign(s);
   assertThat(s.mapsToRegister, is(r));
   assertThat(!s.isSpilled() && s.isTouched() && s.isAllocated(), is(true));
   assertThat(r.mapsToRegister, is(s));
   assertThat(!r.isSpilled() && r.isTouched() && r.isAllocated(), is(true));
   assertThat(ci.isAssigned(regAllocState), is(true));
   assertThat(ci.getAssignment(regAllocState), is(s));
 }