Add test to validate

Author: MaggieKimani1

test/Microsoft.OpenApi.Readers.Tests/V3Tests/OpenApiDocumentTests.cs

@@ -9,8 +9,10 @@
 using System.Threading;
 using FluentAssertions;
 using Microsoft.OpenApi.Any;
+using Microsoft.OpenApi.Exceptions;
 using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Models;
+using Microsoft.OpenApi.Readers.Interface;
 using Microsoft.OpenApi.Validations;
 using Microsoft.OpenApi.Validations.Rules;
 using Microsoft.OpenApi.Writers;
@@ -1355,5 +1357,15 @@ public void ValidateExampleShouldNotHaveDataTypeMismatch()
             var warnings = diagnostic.Warnings;
             Assert.False(warnings.Any());
         }
+
+        [Fact]
+        public void ParseDocumetWithWrongReferenceTypeShouldReturnADiagnosticError()
+        {
+            using var stream = Resources.GetStream(Path.Combine(SampleFolderPath, "docWithWrongRef.json"));
+            _ = new OpenApiStreamReader().Read(stream, out var diagnostic);
+
+            diagnostic.Errors.Should().BeEquivalentTo(new List<OpenApiError> {
+                new( new OpenApiException("Invalid Reference Type 'Schema'.")) });
+        }
     }
 }

test/Microsoft.OpenApi.Readers.Tests/V3Tests/Samples/OpenApiDocument/docWithWrongRef.json

@@ -0,0 +1,27 @@
+{
+    "openapi":"3.0.0",
+    "info":{
+        "title":"some api",
+        "description":"some description",
+        "version": "1"
+    },
+    "servers":[{"url":"https://localhost"}],
+    "paths":{
+        "/count":{
+            "get":{
+                "responses":{
+                    "200":{
+                        "$ref":"#/components/schemas/count"
+                    },
+                },
+            }
+        }
+    },
+    "components":{
+        "schemas":{
+            "count":{
+                "type": "number"
+            }
+        }
+    }
+}