code: package it.unibz.inf.ontop.docker.postgres;
  
  import com.google.common.collect.ImmutableList;
  import it.unibz.inf.ontop.docker.AbstractVirtualModeTest;
  import it.unibz.inf.ontop.owlapi.OntopOWLEngine;
  import it.unibz.inf.ontop.owlapi.connection.OntopOWLConnection;
  import it.unibz.inf.ontop.owlapi.connection.OntopOWLStatement;
  import org.junit.AfterClass;
  import org.junit.BeforeClass;
  import org.junit.Test;
  import org.semanticweb.owlapi.model.OWLException;
  import org.semanticweb.owlapi.model.OWLOntologyCreationException;
  
  import java.io.IOException;
  import java.nio.file.Files;
  import java.nio.file.Paths;
  import java.util.stream.Collectors;
  
  /**
   Issue #508
   */
  public class GroupConcatTest extends AbstractVirtualModeTest {
  
      static final String owlfile = "/pgsql/gconcat/vkg.ttl";
      static final String obdafile = "/pgsql/gconcat/vkg.obda";
      static final String propertiesfile = "/pgsql/gconcat/vkg.properties";
  
      private static OntopOWLEngine REASONER;
      private static OntopOWLConnection CONNECTION;
  
      @BeforeClass
      public static void before() throws OWLOntologyCreationException {
          REASONER = createReasoner(owlfile, obdafile, propertiesfile);
          CONNECTION = REASONER.getConnection();
      }
  
      @Override
      protected OntopOWLStatement createStatement() throws OWLException {
          return CONNECTION.createStatement();
      }
  
      @AfterClass
      public static void after() throws Exception {
          CONNECTION.close();
          REASONER.close();
      }
  
      /**
       * @throws Exception
       */
      @Test
      public void testPostgresGroupConcat1() throws Exception {
          String query = readFromFile("/pgsql/gconcat/query1.rq");
          checkReturnedValuesUnordered(ImmutableList.of("Tom"), query);
      }
  
      /**
       * @throws Exception
       */
      @Test
      public void testPostgresGroupConcat2() throws Exception {
          String query = readFromFile("/pgsql/gconcat/query2.rq");
          checkReturnedValuesUnordered(ImmutableList.of("Tom; Tommaso"), query);
      }
  
  
      private String readFromFile(String path) throws IOException {
          return Files.lines(Paths.get(GroupConcatTest.class.getResource(path).getPath()))
                  .collect(Collectors.joining(System.lineSeparator()));
      }
  }
  