diff --git a/python/plugins/processing/tests/testdata/expected/mesh_surface_to_polygon.gml b/python/plugins/processing/tests/testdata/expected/mesh_surface_to_polygon.gml
index 6cca9568f6d5..b15b731e4923 100644
--- a/python/plugins/processing/tests/testdata/expected/mesh_surface_to_polygon.gml
+++ b/python/plugins/processing/tests/testdata/expected/mesh_surface_to_polygon.gml
@@ -2,15 +2,15 @@
 <ogr:FeatureCollection
      gml:id="aFeatureCollection"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-     xsi:schemaLocation="http://ogr.maptools.org/ a.xsd"
+     xsi:schemaLocation="http://ogr.maptools.org/ mesh_surface_to_polygon.xsd"
      xmlns:ogr="http://ogr.maptools.org/"
      xmlns:gml="http://www.opengis.net/gml/3.2">
   <gml:boundedBy><gml:Envelope><gml:lowerCorner>1000 2000</gml:lowerCorner><gml:upperCorner>3000 3000</gml:upperCorner></gml:Envelope></gml:boundedBy>
                                                                                                                                                                                                        
   <ogr:featureMember>
-    <ogr:a gml:id="a.0">
+    <ogr:mesh_surface_to_polygon gml:id="mesh_surface_to_polygon.0">
       <gml:boundedBy><gml:Envelope><gml:lowerCorner>1000 2000</gml:lowerCorner><gml:upperCorner>3000 3000</gml:upperCorner></gml:Envelope></gml:boundedBy>
-      <ogr:geometryProperty><gml:MultiSurface gml:id="a.geom.0"><gml:surfaceMember><gml:Polygon gml:id="a.geom.0.0"><gml:exterior><gml:LinearRing><gml:posList>1000 2000 2000 2000 3000 2000 2000 3000 1000 3000 1000 2000</gml:posList></gml:LinearRing></gml:exterior></gml:Polygon></gml:surfaceMember></gml:MultiSurface></ogr:geometryProperty>
-    </ogr:a>
+      <ogr:geometryProperty><gml:MultiSurface gml:id="mesh_surface_to_polygon.geom.0"><gml:surfaceMember><gml:Polygon gml:id="mesh_surface_to_polygon.geom.0.0"><gml:exterior><gml:LinearRing><gml:posList>1000 2000 2000 2000 3000 2000 2000 3000 1000 3000 1000 2000</gml:posList></gml:LinearRing></gml:exterior></gml:Polygon></gml:surfaceMember></gml:MultiSurface></ogr:geometryProperty>
+    </ogr:mesh_surface_to_polygon>
   </ogr:featureMember>
 </ogr:FeatureCollection>
diff --git a/python/plugins/processing/tests/testdata/expected/mesh_surface_to_polygon.xsd b/python/plugins/processing/tests/testdata/expected/mesh_surface_to_polygon.xsd
new file mode 100644
index 000000000000..21f8960b3e6f
--- /dev/null
+++ b/python/plugins/processing/tests/testdata/expected/mesh_surface_to_polygon.xsd
@@ -0,0 +1,47 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xs:schema 
+    targetNamespace="http://ogr.maptools.org/"
+    xmlns:ogr="http://ogr.maptools.org/"
+    xmlns:xs="http://www.w3.org/2001/XMLSchema"
+    xmlns:gml="http://www.opengis.net/gml/3.2"
+    xmlns:gmlsf="http://www.opengis.net/gmlsf/2.0"
+    elementFormDefault="qualified"
+    version="1.0">
+<xs:annotation>
+  <xs:appinfo source="http://schemas.opengis.net/gmlsfProfile/2.0/gmlsfLevels.xsd">
+    <gmlsf:ComplianceLevel>0</gmlsf:ComplianceLevel>
+  </xs:appinfo>
+</xs:annotation>
+<xs:import namespace="http://www.opengis.net/gml/3.2" schemaLocation="http://schemas.opengis.net/gml/3.2.1/gml.xsd"/>
+<xs:import namespace="http://www.opengis.net/gmlsf/2.0" schemaLocation="http://schemas.opengis.net/gmlsfProfile/2.0/gmlsfLevels.xsd"/>
+<xs:element name="FeatureCollection" type="ogr:FeatureCollectionType" substitutionGroup="gml:AbstractFeature"/>
+<xs:complexType name="FeatureCollectionType">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureType">
+      <xs:sequence minOccurs="0" maxOccurs="unbounded">
+        <xs:element name="featureMember">
+          <xs:complexType>
+            <xs:complexContent>
+              <xs:extension base="gml:AbstractFeatureMemberType">
+                <xs:sequence>
+                  <xs:element ref="gml:AbstractFeature"/>
+                </xs:sequence>
+              </xs:extension>
+            </xs:complexContent>
+          </xs:complexType>
+        </xs:element>
+      </xs:sequence>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+<xs:element name="mesh_surface_to_polygon" type="ogr:mesh_surface_to_polygon_Type" substitutionGroup="gml:AbstractFeature"/>
+<xs:complexType name="mesh_surface_to_polygon_Type">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureType">
+      <xs:sequence>
+        <xs:element name="geometryProperty" type="gml:MultiSurfacePropertyType" nillable="true" minOccurs="0" maxOccurs="1"/> <!-- restricted to MultiPolygon -->
+      </xs:sequence>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+</xs:schema>