@Test
  public void testIntersection() throws ProcessException, NoSuchIdentifierException {

    // Inputs
    final FeatureCollection<?> featureList = buildFeatureList();
    final FeatureCollection<?> featureUnionList = buildFeatureUnionList();

    // Process
    ProcessDescriptor desc = ProcessFinder.getProcessDescriptor("vector", "union");

    ParameterValueGroup in = desc.getInputDescriptor().createValue();
    in.parameter("feature_in").setValue(featureList);
    in.parameter("feature_union").setValue(featureUnionList);
    in.parameter("input_geometry_name").setValue("geom1");
    org.geotoolkit.process.Process proc = desc.createProcess(in);

    // Features out
    final FeatureCollection<?> featureListOut =
        (FeatureCollection<?>) proc.call().parameter("feature_out").getValue();

    // Expected Features out
    final FeatureCollection<?> featureListResult = buildResultList();

    assertEquals(featureListOut.getFeatureType(), featureListResult.getFeatureType());
    assertEquals(featureListOut.getID(), featureListResult.getID());
    assertEquals(featureListOut.size(), featureListResult.size());
    assertTrue(featureListOut.containsAll(featureListResult));
  }
  /**
   * @param featureCollection
   * @param writer
   * @param fragment : true if we write in a stream, dont write start and end elements
   * @throws DataStoreException
   */
  public Element writeFeatureCollection(
      final FeatureCollection featureCollection, final boolean fragment, final boolean wfs)
      throws DataStoreException, ParserConfigurationException {

    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    // then we have to create document-loader:
    factory.setNamespaceAware(false);
    DocumentBuilder loader = factory.newDocumentBuilder();

    // creating a new DOM-document...
    Document document = loader.newDocument();

    // the XML header
    if (!fragment) {
      document.setXmlVersion("1.0");
      // writer.writeStartDocument("UTF-8", "1.0");
    }

    // the root Element
    final Element rootElement;
    if (wfs) {
      rootElement = document.createElementNS("http://www.opengis.net/wfs", "FeatureCollection");
      rootElement.setPrefix("wfs");
    } else {
      rootElement = document.createElementNS("http://www.opengis.net/gml", "FeatureCollection");
      rootElement.setPrefix("gml");
    }

    document.appendChild(rootElement);

    String collectionID = "";
    if (featureCollection.getID() != null) {
      collectionID = featureCollection.getID();
    }
    final Attr idAttribute = document.createAttributeNS(Namespaces.GML, "id");
    idAttribute.setValue(collectionID);
    idAttribute.setPrefix("gml");
    rootElement.setAttributeNodeNS(idAttribute);

    if (schemaLocation != null && !schemaLocation.equals("")) {
      rootElement.setAttributeNS(
          "http://www.w3.org/2001/XMLSchema-instance", "schemaLocation", schemaLocation);
    }

    /*FeatureType type = featureCollection.getFeatureType();
    if (type != null && type.getName() != null) {
        String namespace = type.getName().getNamespaceURI();
        if (namespace != null && !namespace.equals(Namespaces.GML)) {
            Prefix prefix    = getPrefix(namespace);
            writer.writeNamespace(prefix.prefix, namespace);
        }
    }*/
    /*
     * The boundedby part
     */
    final Element boundElement = writeBounds(featureCollection.getEnvelope(), document);
    if (boundElement != null) {
      rootElement.appendChild(boundElement);
    }

    // we write each feature member of the collection
    FeatureIterator iterator = featureCollection.iterator();
    try {
      while (iterator.hasNext()) {
        final Feature f = iterator.next();
        final Element memberElement = document.createElementNS(Namespaces.GML, "featureMember");
        memberElement.setPrefix("gml");
        memberElement.appendChild(writeFeature(f, document, true));
        rootElement.appendChild(memberElement);
      }

    } finally {
      // we close the stream
      iterator.close();
    }
    return rootElement;
  }