Add test and update API

Author: MaggieKimani1

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

@@ -452,5 +452,48 @@ public void SerializeSchemaWithJsonSchemaKeywordsWorks()
             schema.Vocabulary.Keys.Count.Should().Be(5);
             schemaString.MakeLineBreaksEnvironmentNeutral().Should().Be(expected.MakeLineBreaksEnvironmentNeutral());
         }
+
+        [Fact]
+        public void ParseSchemaWithConstWorks()
+        {
+            var expected = @"{
+  ""$schema"": ""https://json-schema.org/draft/2020-12/schema"",
+  ""required"": [
+    ""status""
+  ],
+  ""type"": ""object"",
+  ""properties"": {
+    ""status"": {
+      ""const"": ""active"",
+      ""type"": ""string""
+    },
+    ""user"": {
+      ""required"": [
+        ""role""
+      ],
+      ""type"": ""object"",
+      ""properties"": {
+        ""role"": {
+          ""const"": ""admin"",
+          ""type"": ""string""
+        }
+      }
+    }
+  }
+}";
+
+            var path = Path.Combine(SampleFolderPath, "schemaWithConst.json");
+
+            // Act
+            var schema = OpenApiModelFactory.Load<OpenApiSchema>(path, OpenApiSpecVersion.OpenApi3_1, out _);
+            schema.Properties["status"].Const.Should().Be("active");
+            schema.Properties["user"].Properties["role"].Const.Should().Be("admin");
+
+            // serialization
+            var writer = new StringWriter();
+            schema.SerializeAsV31(new OpenApiJsonWriter(writer));
+            var schemaString = writer.ToString();
+            schemaString.MakeLineBreaksEnvironmentNeutral().Should().Be(expected.MakeLineBreaksEnvironmentNeutral());
+        }
     }
 }

test/Microsoft.OpenApi.Readers.Tests/V31Tests/Samples/OpenApiSchema/schemaWithConst.json

@@ -0,0 +1,21 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "type": "object",
+  "properties": {
+    "status": {
+      "type": "string",
+      "const": "active"
+    },
+    "user": {
+      "type": "object",
+      "properties": {
+        "role": {
+          "type": "string",
+          "const": "admin"
+        }
+      },
+      "required": [ "role" ]
+    }
+  },
+  "required": [ "status" ]
+}

test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt

@@ -398,6 +398,7 @@ namespace Microsoft.OpenApi.Models
         public const string Comment = "$comment";
         public const string Components = "components";
         public const string ComponentsSegment = "/components/";
+        public const string Const = "const";
         public const string Consumes = "consumes";
         public const string Contact = "contact";
         public const string Content = "content";
@@ -882,6 +883,7 @@ namespace Microsoft.OpenApi.Models
         public virtual System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiSchema> AllOf { get; set; }
         public virtual System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiSchema> AnyOf { get; set; }
         public virtual string Comment { get; set; }
+        public virtual string Const { get; set; }
         public virtual System.Text.Json.Nodes.JsonNode Default { get; set; }
         public virtual System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiSchema> Definitions { get; set; }
         public virtual bool Deprecated { get; set; }
@@ -1222,6 +1224,7 @@ namespace Microsoft.OpenApi.Models.References
         public override System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiSchema> AllOf { get; set; }
         public override System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiSchema> AnyOf { get; set; }
         public override string Comment { get; set; }
+        public override string Const { get; set; }
         public override System.Text.Json.Nodes.JsonNode Default { get; set; }
         public override System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiSchema> Definitions { get; set; }
         public override bool Deprecated { get; set; }