Add test

Author: MaggieKimani1

src/Microsoft.OpenApi/Services/CopyReferences.cs

@@ -110,6 +110,7 @@ public override void Visit(IOpenApiReferenceable referenceable)
                 default:
                     break;
             }
+
             base.Visit(referenceable);
         }
 

test/Microsoft.OpenApi.Hidi.Tests/Microsoft.OpenApi.Hidi.Tests.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>net8.0</TargetFramework>
@@ -34,4 +34,10 @@
     </Compile>
   </ItemGroup>
 
+  <ItemGroup>
+    <None Update="UtilityFiles\docWithReusableHeadersAndExamples.yaml">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+  </ItemGroup>
+
 </Project>

test/Microsoft.OpenApi.Hidi.Tests/Services/OpenApiFilterServiceTests.cs

@@ -3,9 +3,11 @@
 
 using Microsoft.Extensions.Logging;
 using Microsoft.OpenApi.Models;
+using Microsoft.OpenApi.Readers;
 using Microsoft.OpenApi.Services;
 using Microsoft.OpenApi.Tests.UtilityFiles;
 using Moq;
+using SharpYaml.Tokens;
 using Xunit;
 
 namespace Microsoft.OpenApi.Hidi.Tests
@@ -170,6 +172,33 @@ public void ThrowsInvalidOperationExceptionInCreatePredicateWhenInvalidArguments
             Assert.Equal("Cannot specify both operationIds and tags at the same time.", message2);
         }
 
+        [Fact]
+        public void CopiesOverAllReferencedComponentsToTheSubsetDocumentCorrectly()
+        {
+            // Arrange
+            var filePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "UtilityFiles", "docWithReusableHeadersAndExamples.yaml");
+            var operationIds = "getItems";
+
+            // Act
+            using var stream = File.OpenRead(filePath);
+            var doc = new OpenApiStreamReader().Read(stream, out var diagnostic);
+            
+            var predicate = OpenApiFilterService.CreatePredicate(operationIds: operationIds);
+            var subsetOpenApiDocument = OpenApiFilterService.CreateFilteredDocument(doc, predicate);
+
+            var response = subsetOpenApiDocument.Paths["/items"].Operations[OperationType.Get].Responses["200"];
+            var responseHeader = response.Headers["x-custom-header"];
+            var mediaTypeExample = response.Content["application/json"].Examples.First().Value;
+            var targetHeaders = subsetOpenApiDocument.Components.Headers;
+            var targetExamples = subsetOpenApiDocument.Components.Examples;
+
+            // Assert
+            Assert.False(responseHeader.UnresolvedReference);
+            Assert.False(mediaTypeExample.UnresolvedReference);
+            Assert.Single(targetHeaders);
+            Assert.Single(targetExamples);
+        }
+
         [Theory]
         [InlineData("reports.getTeamsUserActivityUserDetail-a3f1", null)]
         [InlineData(null, "reports.Functions")]

test/Microsoft.OpenApi.Hidi.Tests/UtilityFiles/docWithReusableHeadersAndExamples.yaml

@@ -0,0 +1,79 @@
+openapi: 3.0.1
+info:
+  title: Example with Multiple Operations and Local $refs
+  version: 1.0.0
+paths:
+  /items:
+    get:
+      operationId: getItems
+      summary: Get a list of items
+      responses:
+        '200':
+          description: A list of items
+          headers:
+            x-custom-header:
+               $ref: '#/components/headers/CustomHeader'
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  type: string
+              examples:
+                ItemExample:
+                  $ref: '#/components/examples/ItemExample'
+    post:
+      operationId: createItem
+      summary: Create a new item
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                name:
+                  type: string
+              example:
+                $ref: '#/components/examples/ItemExample'
+      responses:
+        '201':
+          description: Item created
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  id:
+                    type: string
+                  name:
+                    type: string
+              example:
+                $ref: '#/components/examples/ItemExample'
+components:
+  schemas:
+    pet:
+      type: object
+      required:
+        - id
+        - name
+      properties:
+        id:
+          type: integer
+          format: int64
+        name:
+          type: string
+        tag:
+           type: string
+  headers:
+    CustomHeader:
+      description: Custom header for authentication
+      required: true
+      schema:
+        type: string
+  examples:
+    ItemExample:
+      summary: Example of a new item to be created
+      value:
+        name: "New Item"
+