Adding test to Line Intersection algorithm

Since both input and intersect layers have only one field (fid), the result is the same for both (existing and new) tests. The result now comes with the intersect field, renamed to fid_1 (previously not kept).

python/plugins/processing/tests/testdata/expected/line_intersection.gfs

@@ -2,6 +2,7 @@
   <GMLFeatureClass>
     <Name>line_intersection</Name>
     <ElementPath>line_intersection</ElementPath>
+    <!--POINT-->
     <GeometryType>1</GeometryType>
     <SRSName>EPSG:4326</SRSName>
     <DatasetSpecificInfo>
@@ -11,5 +12,10 @@
       <ExtentYMin>-0.22085</ExtentYMin>
       <ExtentYMax>3.22098</ExtentYMax>
     </DatasetSpecificInfo>
+    <PropertyDefn>
+      <Name>fid_1</Name>
+      <ElementPath>fid_1</ElementPath>
+      <Type>Integer</Type>
+    </PropertyDefn>
   </GMLFeatureClass>
 </GMLFeatureClassList>

python/plugins/processing/tests/testdata/expected/line_intersection.gml

@@ -13,22 +13,26 @@
 
   <gml:featureMember>
     <ogr:line_intersection fid="lines.0">
-      <ogr:geometryProperty><gml:Point srsName="EPSG:4326"><gml:coordinates>9.220978076442222,3.220978076442222</gml:coordinates></gml:Point></ogr:geometryProperty>
+      <ogr:geometryProperty><gml:Point srsName="EPSG:4326"><gml:coordinates>9.22097807644222,3.22097807644222</gml:coordinates></gml:Point></ogr:geometryProperty>
+      <ogr:fid_1>3</ogr:fid_1>
     </ogr:line_intersection>
   </gml:featureMember>
   <gml:featureMember>
     <ogr:line_intersection fid="lines.2">
       <ogr:geometryProperty><gml:Point srsName="EPSG:4326"><gml:coordinates>3.0,2.8034726769992</gml:coordinates></gml:Point></ogr:geometryProperty>
+      <ogr:fid_1>3</ogr:fid_1>
     </ogr:line_intersection>
   </gml:featureMember>
   <gml:featureMember>
     <ogr:line_intersection fid="lines.3">
-      <ogr:geometryProperty><gml:Point srsName="EPSG:4326"><gml:coordinates>3.155795677799609,1.0</gml:coordinates></gml:Point></ogr:geometryProperty>
+      <ogr:geometryProperty><gml:Point srsName="EPSG:4326"><gml:coordinates>3.15579567779961,1.0</gml:coordinates></gml:Point></ogr:geometryProperty>
+      <ogr:fid_1>2</ogr:fid_1>
     </ogr:line_intersection>
   </gml:featureMember>
   <gml:featureMember>
     <ogr:line_intersection fid="lines.5">
-      <ogr:geometryProperty><gml:Point srsName="EPSG:4326"><gml:coordinates>8.779149848187174,-0.220850151812825</gml:coordinates></gml:Point></ogr:geometryProperty>
+      <ogr:geometryProperty><gml:Point srsName="EPSG:4326"><gml:coordinates>8.77914984818717,-0.220850151812825</gml:coordinates></gml:Point></ogr:geometryProperty>
+      <ogr:fid_1>2</ogr:fid_1>
     </ogr:line_intersection>
   </gml:featureMember>
 </ogr:FeatureCollection>

python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml

@@ -1137,8 +1137,9 @@ tests:
         hash: 7fe0e0174185fd743e23760f33615adf10f771b4275f320db6f7f4f8
         type: rasterhash
 
+  # Case 1: Keep all fields
   - algorithm: qgis:lineintersections
-    name: Line intersection
+    name: Line Intersection Keep All Fields from Both
     params:
       INPUT_A:
         name: lines.gml
@@ -1150,6 +1151,23 @@ tests:
       OUTPUT:
         name: expected/line_intersection.gml
         type: vector
+
+  # Case 2: Keep fid field from both layers
+  - algorithm: qgis:lineintersections
+    name: Line Intersection Keep fid from Both
+    params:
+      FIELD_A: fid
+      FIELD_B: fid
+      INPUT_A:
+        name: lines.gml
+        type: vector
+      INPUT_B:
+        name: simplify_lines.gml
+        type: vector
+    results:
+      OUTPUT:
+        name: expected/line_intersection.gml
+        type: vector
 
   - algorithm: qgis:sumlinelengths
     name: Sum line lengths