assertTrue(ex.getMessage().contains("refresh failed"));
    }

    @ParameterizedTest
    @MethodSource("domains")
    @DisplayName("getUserDomain handles null and empty")
    void getUserDomain_edges(String domain) {
        TestCredentials creds = new TestCredentials(domain, false, false, new Subject(), false);
        assertEquals(domain, creds.getUserDomain());
    }

    static Stream<String> domains() {