@Test
public void addHead() {

    final ImmutableAuthorizationContext initialContext = ImmutableAuthorizationContext.of(KNOWN_TYPE, SUBJECTS_1);
    final AuthorizationContext newContext = initialContext.addHead(SUBJECTS_2);
    final List<AuthorizationSubject> expectedAuthSubjects = Lists.newArrayList(SUBJECTS_2);
    expectedAuthSubjects.addAll(SUBJECTS_1);
    final ImmutableAuthorizationContext expectedContext =
            ImmutableAuthorizationContext.of(KNOWN_TYPE, expectedAuthSubjects);
    assertThat(newContext).isEqualTo(expectedContext);
}