ClientBuilderTest.java

package com.clickhouse.client.api;

import org.testng.Assert;
import org.testng.annotations.Test;

import java.lang.reflect.Field;
import java.util.List;

public class ClientBuilderTest {

    @Test
    public void testAddEndpointToleratesUnderscoreHostname() throws Exception {
        try (Client client = new Client.Builder()
                .addEndpoint("http://host_with_underscore:8123")
                .setUsername("default")
                .setPassword("")
                .build()) {

            String firstEndpoint = extractFirstEndpointUri(client);
            Assert.assertEquals(firstEndpoint, "http://host_with_underscore:8123/",
                    "Endpoint URI should preserve original hostname");
        }
    }

    private static String extractFirstEndpointUri(Client client) throws Exception {
        Field endpointsField = Client.class.getDeclaredField("endpoints");
        endpointsField.setAccessible(true);

        @SuppressWarnings("unchecked")
        List<com.clickhouse.client.api.transport.Endpoint> endpoints =
                (List<com.clickhouse.client.api.transport.Endpoint>) endpointsField.get(client);
        return endpoints.get(0).getURI().toString();
    }
}