@Test
    void verifyOperation() throws Throwable {
        val kmf = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
        val ks = KeyStore.getInstance("JKS");
        ks.load(null, "changeit".toCharArray());
        kmf.init(ks, "changeit".toCharArray());
        val km = kmf.getKeyManagers();

        val managers = Arrays.stream(km)
            .filter(X509KeyManager.class::isInstance)
            .map(X509KeyManager.class::cast)
            .collect(Collectors.toList());

        val input = new CompositeX509KeyManager(managers);
        assertNull(input.chooseClientAlias(new String[]{"any"}, new Principal[]{}, mock(Socket.class)));
        assertNull(input.chooseServerAlias("any", new Principal[]{}, mock(Socket.class)));
        assertNull(input.getCertificateChain("cas"));
        assertEquals(0, input.getClientAliases("cas", new Principal[]{}).length);
        assertEquals(0, input.getServerAliases("cas", new Principal[]{}).length);

    }
This is {@link CompositeX509KeyManagerTests}.

@author Misagh Moayyed
@since 6.2.0
core/cas-server-core-util-api/src/test/java/org/apereo/cas/util/ssl/CompositeX509KeyManagerTests.java