diff --git a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gfs b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gfs
deleted file mode 100644
index a8c2eef2aaf..00000000000
--- a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gfs
+++ /dev/null
@@ -1,15 +0,0 @@
-<GMLFeatureClassList>
-  <GMLFeatureClass>
-    <Name>single_sided_buffer_line</Name>
-    <ElementPath>single_sided_buffer_line</ElementPath>
-    <GeometryType>3</GeometryType>
-    <SRSName>EPSG:4326</SRSName>
-    <DatasetSpecificInfo>
-      <FeatureCount>7</FeatureCount>
-      <ExtentXMin>-1.00000</ExtentXMin>
-      <ExtentXMax>11.00000</ExtentXMax>
-      <ExtentYMin>-3.00000</ExtentYMin>
-      <ExtentYMax>5.70711</ExtentYMax>
-    </DatasetSpecificInfo>
-  </GMLFeatureClass>
-</GMLFeatureClassList>
diff --git a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gml b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gml
index d1158aeeba2..fb108d1a301 100644
--- a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gml
+++ b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <ogr:FeatureCollection
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-     xsi:schemaLocation=""
+     xsi:schemaLocation="http://ogr.maptools.org/ single_sided_buffer_line.xsd"
      xmlns:ogr="http://ogr.maptools.org/"
      xmlns:gml="http://www.opengis.net/gml">
   <gml:boundedBy>
@@ -13,7 +13,7 @@
                                                                                                                                              
   <gml:featureMember>
     <ogr:single_sided_buffer_line fid="lines.0">
-      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>11,5 9,3 9,2 6,2 6,3 8,3 8.01921471959677,3.195090322016128 8.076120467488714,3.38268343236509 8.168530387697455,3.555570233019602 8.292893218813452,3.707106781186547 10.292893218813452,5.707106781186548 11,5</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>11,5 9,3 9,2 6,2 6,3 8,3 8.01921471959677,3.19509032201613 8.07612046748871,3.38268343236509 8.16853038769746,3.5555702330196 8.29289321881345,3.70710678118655 10.2928932188135,5.70710678118655 11,5</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
     </ogr:single_sided_buffer_line>
   </gml:featureMember>
   <gml:featureMember>
@@ -23,7 +23,7 @@
   </gml:featureMember>
   <gml:featureMember>
     <ogr:single_sided_buffer_line fid="lines.2">
-      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>3,3 3,2 2,2 2,0 1,0 1,2 1.01921471959677,2.195090322016128 1.076120467488713,2.38268343236509 1.168530387697455,2.555570233019602 1.292893218813453,2.707106781186547 1.444429766980398,2.831469612302545 1.61731656763491,2.923879532511287 1.804909677983872,2.98078528040323 2,3 3,3</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>3,3 3,2 2,2 2,0 1,0 1,2 1.01921471959677,2.19509032201613 1.07612046748871,2.38268343236509 1.16853038769745,2.5555702330196 1.29289321881345,2.70710678118655 1.4444297669804,2.83146961230255 1.61731656763491,2.92387953251129 1.80490967798387,2.98078528040323 2,3 3,3</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
     </ogr:single_sided_buffer_line>
   </gml:featureMember>
   <gml:featureMember>
@@ -38,7 +38,7 @@
   </gml:featureMember>
   <gml:featureMember>
     <ogr:single_sided_buffer_line fid="lines.5">
-      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>10,1 6,-3 5.292893218813452,-2.292893218813453 9.292893218813452,1.707106781186547 10,1</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>10,1 6,-3 5.29289321881345,-2.29289321881345 9.29289321881345,1.70710678118655 10,1</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
     </ogr:single_sided_buffer_line>
   </gml:featureMember>
   <gml:featureMember>
diff --git a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.xsd b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.xsd
new file mode 100644
index 00000000000..874e6853497
--- /dev/null
+++ b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.xsd
@@ -0,0 +1,23 @@
+<?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" elementFormDefault="qualified" version="1.0">
+<xs:import namespace="http://www.opengis.net/gml" schemaLocation="http://schemas.opengis.net/gml/2.1.2/feature.xsd"/>
+<xs:element name="FeatureCollection" type="ogr:FeatureCollectionType" substitutionGroup="gml:_FeatureCollection"/>
+<xs:complexType name="FeatureCollectionType">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureCollectionType">
+      <xs:attribute name="lockId" type="xs:string" use="optional"/>
+      <xs:attribute name="scope" type="xs:string" use="optional"/>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+<xs:element name="single_sided_buffer_line" type="ogr:single_sided_buffer_line_Type" substitutionGroup="gml:_Feature"/>
+<xs:complexType name="single_sided_buffer_line_Type">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureType">
+      <xs:sequence>
+        <xs:element name="geometryProperty" type="gml:PolygonPropertyType" nillable="true" minOccurs="0" maxOccurs="1"/>
+      </xs:sequence>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+</xs:schema>