ESQL: Adds a test and fixes running the CsvTestsDataLoader.main (#109836)

Author: astefan

x-pack/plugin/esql/build.gradle

@@ -28,7 +28,9 @@ dependencies {
   // Also contains a dummy processor to allow compilation with unused annotations.
   annotationProcessor project('compute:gen')
 
-  testImplementation project('qa:testFixtures')
+  testImplementation(project('qa:testFixtures')) {
+    exclude(group:"org.elasticsearch.plugin", module: "esql")
+  }
   testImplementation project(':test:framework')
   testImplementation(testArtifact(project(xpackModule('core'))))
   testImplementation project(path: xpackModule('enrich'))

x-pack/plugin/esql/qa/testFixtures/build.gradle

@@ -1,17 +1,24 @@
 apply plugin: 'elasticsearch.java'
-
+apply plugin: org.elasticsearch.gradle.dependencies.CompileOnlyResolvePlugin
 
 dependencies {
     implementation project(':x-pack:plugin:esql:compute')
-    compileOnly project(':x-pack:plugin:esql')
+    implementation project(':x-pack:plugin:esql')
     compileOnly project(path: xpackModule('core'))
     implementation project(":libs:elasticsearch-x-content")
     implementation project(':client:rest')
     implementation project(':libs:elasticsearch-logging')
     implementation project(':test:framework')
     api(testArtifact(project(xpackModule('esql-core'))))
     implementation project(':server')
-    api "net.sf.supercsv:super-csv:${versions.supercsv}"
+    implementation "net.sf.supercsv:super-csv:${versions.supercsv}"
+}
+
+/**
+ * This is needed for CsvTestsDataLoaderTests to reflect the classpath that CsvTestsDataLoader actually uses when "main" method is executed.
+ */
+tasks.named("test").configure {
+  classpath = classpath - (configurations.resolveableCompileOnly - configurations.runtimeClasspath)
 }
 
 /**

x-pack/plugin/esql/qa/testFixtures/src/test/java/org/elasticsearch/xpack/esql/CsvTestsDataLoaderTests.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.esql;
+
+import org.elasticsearch.test.ESTestCase;
+
+import java.net.ConnectException;
+
+import static org.hamcrest.Matchers.startsWith;
+
+public class CsvTestsDataLoaderTests extends ESTestCase {
+
+    public void testCsvTestsDataLoaderExecution() {
+        ConnectException ce = expectThrows(ConnectException.class, () -> CsvTestsDataLoader.main(new String[] {}));
+        assertThat(ce.getMessage(), startsWith("Connection refused"));
+    }
+}