Add tests for slnf template with --parent-solution and -s parameters

Co-authored-by: baronfel <[email protected]>

Author: Copilot

test/dotnet-new.IntegrationTests/Approvals/AllCommonItemsCreate.-o#Solution-Filter-File#-n#item#--parent-solution#Parent.slnx.verified/Solution-Filter-File/item.slnf

@@ -0,0 +1,6 @@
+{
+    "solution": {
+        "path": "Parent.slnx",
+        "projects": []
+    }
+}

test/dotnet-new.IntegrationTests/Approvals/AllCommonItemsCreate.-o#Solution-Filter-File#-n#item#--parent-solution#Parent.slnx.verified/std-streams/stdout.txt

@@ -0,0 +1 @@
+The template "%TEMPLATE_NAME%" was created successfully.

test/dotnet-new.IntegrationTests/Approvals/AllCommonItemsCreate.-o#Solution-Filter-File#-n#item#-s#Parent.slnx.verified/Solution-Filter-File/item.slnf

@@ -0,0 +1,6 @@
+{
+    "solution": {
+        "path": "Parent.slnx",
+        "projects": []
+    }
+}

test/dotnet-new.IntegrationTests/Approvals/AllCommonItemsCreate.-o#Solution-Filter-File#-n#item#-s#Parent.slnx.verified/std-streams/stdout.txt

@@ -0,0 +1 @@
+The template "%TEMPLATE_NAME%" was created successfully.

test/dotnet-new.IntegrationTests/CommonTemplatesTests.cs

@@ -46,6 +46,9 @@ public CommonTemplatesTests(SharedHomeDirectory fixture, ITestOutputHelper log)
         [InlineData("Solution File", "sln", new[] { "--format", "sln" })]
         [InlineData("Solution File", "sln", new[] { "--format", "slnx" })]
         [InlineData("Solution File", "solution", null)]
+        [InlineData("Solution Filter File", "slnf", new[] { "--parent-solution", "Parent.slnx" })]
+        [InlineData("Solution Filter File", "slnf", new[] { "-s", "Parent.slnx" })]
+        [InlineData("Solution Filter File", "solutionfilter", new[] { "--parent-solution", "Parent.slnx" })]
         [InlineData("Dotnet local tool manifest file", "tool-manifest", null)]
         [InlineData("Web Config", "webconfig", null)]
         [InlineData("EditorConfig file", "editorconfig", null)]