resolve the comments, typos and some test codes

Author: xuzhg

src/Microsoft.OpenApi/Validations/Rules/OpenApiExternalDocsRules.cs

@@ -20,7 +20,7 @@ internal static class OpenApiExternalDocsRules
             new ValidationRule<OpenApiExternalDocs>(
                 (context, item) =>
                 {
-                    // title
+                    // url
                     context.Push("url");
                     if (item.Url == null)
                     {

src/Microsoft.OpenApi/Validations/Rules/OpenApiPathsRules.cs

@@ -13,7 +13,7 @@ namespace Microsoft.OpenApi.Validations.Rules
     public static class OpenApiPathsRules
     {
         /// <summary>
-        /// A relative path to an individual endpoint. The field name MUST begin with a slash. 
+        /// A relative path to an individual endpoint. The field name MUST begin with a slash.
         /// </summary>
         public static ValidationRule<OpenApiPaths> PathNameMustBeginWithSlash =>
             new ValidationRule<OpenApiPaths>(

src/Microsoft.OpenApi/Validations/Rules/OpenApiResponseRules.cs

@@ -20,7 +20,7 @@ internal static class OpenApiResponseRules
             new ValidationRule<OpenApiResponse>(
                 (context, response) =>
                 {
-                    // title
+                    // description
                     context.Push("description");
                     if (String.IsNullOrEmpty(response.Description))
                     {

src/Microsoft.OpenApi/Validations/Rules/OpenApiServerRules.cs

@@ -14,7 +14,7 @@ namespace Microsoft.OpenApi.Validations.Rules
     public static class OpenApiServerRules
     {
         /// <summary>
-        /// REQUIRED.
+        /// Validate the field is required.
         /// </summary>
         public static ValidationRule<OpenApiServer> FieldIsRequired =>
             new ValidationRule<OpenApiServer>(

src/Microsoft.OpenApi/Validations/Rules/OpenApiTagRules.cs

@@ -14,7 +14,7 @@ namespace Microsoft.OpenApi.Validations.Rules
     public static class OpenApiTagRules
     {
         /// <summary>
-        /// REQUIRED.
+        /// Validate the field is required.
         /// </summary>
         public static ValidationRule<OpenApiTag> FieldIsRequired =>
             new ValidationRule<OpenApiTag>(

src/Microsoft.OpenApi/Validations/Rules/RuleHelpers.cs

@@ -11,7 +11,7 @@ internal static class RuleHelpers
         /// Input string must be in the format of an email address
         /// </summary>
         /// <param name="input">The input string.</param>
-        /// <returns></returns>
+        /// <returns>True if it's an email address. Otherwise False.</returns>
         public static bool IsEmailAddress(this string input)
         {
             if (String.IsNullOrEmpty(input))

src/Microsoft.OpenApi/Validations/ValidationError.cs

@@ -58,7 +58,7 @@ public ValidationError(ErrorReason reason, string path, string message)
         /// <returns>The error string.</returns>
         public override string ToString()
         {
-            return "ErroCode: " + ErrorCode + ", " + ErrorPath + " | " + ErrorMessage;
+            return "ErrorCode: " + ErrorCode + ", " + ErrorPath + " | " + ErrorMessage;
         }
     }
 }

src/Microsoft.OpenApi/Validations/Visitors/VisitorBase.cs

@@ -38,13 +38,13 @@ public void Visit(ValidationContext context, object item)
         /// <param name="element">The element.</param>
         protected virtual void Next(ValidationContext context, T element)
         {
-            IOpenApiExtensible extensbile = element as IOpenApiExtensible;
-            if (extensbile != null)
+            IOpenApiExtensible extensible = element as IOpenApiExtensible;
+            if (extensible != null)
             {
                 var rules = context.RuleSet.Where(r => r.ElementType == typeof(IOpenApiExtensible));
                 foreach (var rule in rules)
                 {
-                    rule.Evaluate(context, extensbile);
+                    rule.Evaluate(context, extensible);
                 }
             }
         }

test/Microsoft.OpenApi.Tests/Validations/OpenApiResponseValidationTests.cs

@@ -24,6 +24,8 @@ public void ValidateDescriptionIsRequiredInResponse()
             Assert.NotNull(errors);
             ValidationError error = Assert.Single(errors);
             Assert.Equal("The field 'description' in 'response' object is REQUIRED.", error.ErrorMessage);
+            Assert.Equal(ErrorReason.Required, error.ErrorCode);
+            Assert.Equal("#/description", error.ErrorPath);
         }
     }
 }

test/Microsoft.OpenApi.Tests/Validations/Visitors/OpenApiVisitorSetTests.cs

@@ -21,7 +21,7 @@ public void VisitorsPropertyReturnsTheCorrectVisitorList()
                 // Assert
                 Assert.NotNull(visitors);
                 Assert.NotEmpty(visitors);
-                Assert.Equal(29, visitors.Count);
+                Assert.Equal(29, visitors.Count); // Now, we have 29 DOM classes.
             }
         }
 
@@ -38,10 +38,35 @@ public void GetVisitorThrowsUnknowElementType()
         }
 
         [Theory]
+        [InlineData(typeof(OpenApiCallback), typeof(CallbackVisitor))]
+        [InlineData(typeof(OpenApiComponents), typeof(ComponentsVisitor))]
+        [InlineData(typeof(OpenApiContact), typeof(ContactVisitor))]
+        [InlineData(typeof(OpenApiDiscriminator), typeof(DiscriminatorVisitor))]
         [InlineData(typeof(OpenApiDocument), typeof(DocumentVisitor))]
+        [InlineData(typeof(OpenApiEncoding), typeof(EncodingVisitor))]
+        [InlineData(typeof(OpenApiExample), typeof(ExampleVisitor))]
+        [InlineData(typeof(OpenApiExternalDocs), typeof(ExternalDocsVisitor))]
+        [InlineData(typeof(OpenApiHeader), typeof(HeaderVisitor))]
         [InlineData(typeof(OpenApiInfo), typeof(InfoVisitor))]
+        [InlineData(typeof(OpenApiLicense), typeof(LicenseVisitor))]
+        [InlineData(typeof(OpenApiLink), typeof(LinkVisitor))]
+        [InlineData(typeof(OpenApiMediaType), typeof(MediaTypeVisitor))]
+        [InlineData(typeof(OpenApiOAuthFlows), typeof(OAuthFlowsVisitor))]
+        [InlineData(typeof(OpenApiOAuthFlow), typeof(OAuthFlowVisitor))]
+        [InlineData(typeof(OpenApiOperation), typeof(OperationVisitor))]
+        [InlineData(typeof(OpenApiParameter), typeof(ParameterVisitor))]
+        [InlineData(typeof(OpenApiPathItem), typeof(PathItemVisitor))]
+        [InlineData(typeof(OpenApiPaths), typeof(PathsVisitor))]
+        [InlineData(typeof(OpenApiRequestBody), typeof(RequestBodyVisitor))]
+        [InlineData(typeof(OpenApiResponses), typeof(ResponsesVisitor))]
+        [InlineData(typeof(OpenApiResponse), typeof(ResponseVisitor))]
+        [InlineData(typeof(OpenApiSchema), typeof(SchemaVisitor))]
+        [InlineData(typeof(OpenApiSecurityRequirement), typeof(SecurityRequirementVisitor))]
+        [InlineData(typeof(OpenApiSecurityScheme), typeof(SecuritySchemeVisitor))]
+        [InlineData(typeof(OpenApiServerVariable), typeof(ServerVariableVisitor))]
+        [InlineData(typeof(OpenApiServer), typeof(ServerVisitor))]
+        [InlineData(typeof(OpenApiTag), typeof(TagVisitor))]
         [InlineData(typeof(OpenApiXml), typeof(XmlVisitor))]
-        [InlineData(typeof(OpenApiComponents), typeof(ComponentsVisitor))]
         public void GetVisitorReturnsTheCorrectVisitor(Type elementType, Type visitorType)
         {
             // Arrange & Act