@Test
public void getAssertion_ValidSecurityContextHolder_Assertion() {

    String user = "casuser";
    String ticket = "ST-21-c1gk6jBcfYnatLbNExfx-0623277bc36a";
    Set<SimpleGrantedAuthority> roles = Collections.singleton(new SimpleGrantedAuthority("MEMBER"));
    CasAuthenticationToken authentication = new CasAuthenticationToken(UUID.randomUUID().toString(), user,
            ticket, roles, new User(user, ticket, roles), new AssertionImpl(user));
    SecurityContextHolder.getContext().setAuthentication(authentication);
    AssertionProvider provider = new SecurityContextHolderAssertionProvider();
    assertThat(provider.getAssertion()).isNotNull();
    assertThat(provider.getAssertion().getPrincipal().getName()).isEqualTo(user);
}