chore: adds unit tests for tags reference parsing

Signed-off-by: Vincent Biret <[email protected]>

Author: baywet

test/Microsoft.OpenApi.Readers.Tests/V31Tests/OpenApiTagReferenceDeserializerTests.cs

@@ -0,0 +1,47 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.Json.Nodes;
+using Microsoft.OpenApi.Reader;
+using Microsoft.OpenApi.Reader.V31;
+using Xunit;
+
+namespace Microsoft.OpenApi.Readers.Tests.V31Tests;
+
+public class OpenApiTagReferenceDeserializerTests
+{
+    [Fact]
+    public void ShouldDeserializeTagReferenceAnnotations()
+    {
+        var json =
+        """
+        {
+            "tags" : [
+                "MyTag"
+            ]
+        }
+        """;
+
+        var hostDocument = new OpenApiDocument();
+        hostDocument.Tags ??= new HashSet<OpenApiTag>();
+        hostDocument.Tags.Add(new OpenApiTag
+        {
+            Name = "MyTag",
+            Description = "This is a tag description",
+        });
+        var jsonNode = JsonNode.Parse(json);
+        var parseNode = ParseNode.Create(new ParsingContext(new()), jsonNode);
+
+        var result = OpenApiV31Deserializer.LoadOperation(parseNode, hostDocument);
+        // this diverges from the other unit tests because Tag References are implemented
+        // through the reference infrastructure for convenience, but the behave quite differently
+
+        Assert.NotNull(result);
+        Assert.NotNull(result.Tags);
+        Assert.Single(result.Tags);
+        var resultReference = Assert.IsType<OpenApiTagReference>(result.Tags.First());
+
+        Assert.Equal("MyTag", resultReference.Reference.Id);
+        Assert.Equal("This is a tag description", resultReference.Description);
+        Assert.NotNull(resultReference.Target);
+    }
+}