@ParameterizedTest
    @ArgumentsSource(SslTransportLayerArgumentsProvider.class)
    public void testPemFilesWithoutClientKeyPassword(Args args) throws Exception {
        boolean useInlinePem = args.useInlinePem;
        TestSslUtils.convertToPem(args.sslServerConfigs, !useInlinePem, true);
        TestSslUtils.convertToPem(args.sslClientConfigs, !useInlinePem, false);
        args.sslServerConfigs.put(BrokerSecurityConfigs.SSL_CLIENT_AUTH_CONFIG, "required");
        verifySslConfigs(args);
    }
Test with PEM key store files without key password for client key store.
clients/src/test/java/org/apache/kafka/common/network/SslTransportLayerTest.java