test(reader): add nullable-before-type tests for V3.0 and V3.2

Agent-Logs-Url: https://github.com/microsoft/OpenAPI.NET/sessions/6de5cea9-ff8f-4a95-804d-493007f279f3

Co-authored-by: baywet <7905502+baywet@users.noreply.github.com>

Author: Copilot

test/Microsoft.OpenApi.Readers.Tests/V32Tests/OpenApiSchemaTests.cs

@@ -131,6 +131,18 @@ public void ParseSchemaWithTypeArrayWorks()
             Assert.Equivalent(expected, actual);
         }
 
+        [Theory]
+        [InlineData(@"{ ""nullable"": true, ""type"": ""string"" }")]
+        [InlineData(@"{ ""type"": ""string"", ""nullable"": true }")]
+        public void ParseSchemaWithNullableBeforeOrAfterTypePreservesNullFlag(string schemaJson)
+        {
+            // Act
+            var schema = OpenApiModelFactory.Parse<OpenApiSchema>(schemaJson, OpenApiSpecVersion.OpenApi3_2, new(), out _, "json", SettingsFixture.ReaderSettings);
+
+            // Assert
+            Assert.Equal(JsonSchemaType.String | JsonSchemaType.Null, schema.Type);
+        }
+
         [Fact]
         public void TestSchemaCopyConstructorWithTypeArrayWorks()
         {

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

@@ -133,6 +133,18 @@ public void ParsePathFragmentShouldSucceed()
                 }, openApiAny);
         }
 
+        [Theory]
+        [InlineData(@"{ ""nullable"": true, ""type"": ""string"" }")]
+        [InlineData(@"{ ""type"": ""string"", ""nullable"": true }")]
+        public void ParseSchemaWithNullableBeforeOrAfterTypePreservesNullFlag(string schemaJson)
+        {
+            // Act
+            var schema = OpenApiModelFactory.Parse<OpenApiSchema>(schemaJson, OpenApiSpecVersion.OpenApi3_0, new(), out _, "json", SettingsFixture.ReaderSettings);
+
+            // Assert
+            Assert.Equal(JsonSchemaType.String | JsonSchemaType.Null, schema.Type);
+        }
+
         [Fact]
         public void ParseDictionarySchemaShouldSucceed()
         {