diff --git a/Directory.Build.props b/Directory.Build.props
index 9937770d..13eb4ee4 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -4,7 +4,7 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <VersionPrefix>1.0.19</VersionPrefix>
+    <VersionPrefix>1.0.20</VersionPrefix>
   </PropertyGroup>
 
   <Choose>
diff --git a/GitHubReleaseNotes.txt b/GitHubReleaseNotes.txt
index 5dd7de2e..88cae14c 100644
--- a/GitHubReleaseNotes.txt
+++ b/GitHubReleaseNotes.txt
@@ -1,3 +1,3 @@
 https://github.com/StefH/GitHubReleaseNotes
 
-GitHubReleaseNotes.exe --output CHANGELOG.md --skip-empty-releases --version 1.0.19.0
\ No newline at end of file
+GitHubReleaseNotes.exe --output CHANGELOG.md --skip-empty-releases --version 1.0.20.0
\ No newline at end of file
diff --git a/src/WireMock.Net/Admin/Mappings/MappingModel.cs b/src/WireMock.Net/Admin/Mappings/MappingModel.cs
index 2e005729..f5eb8afe 100644
--- a/src/WireMock.Net/Admin/Mappings/MappingModel.cs
+++ b/src/WireMock.Net/Admin/Mappings/MappingModel.cs
@@ -39,13 +39,18 @@ namespace WireMock.Admin.Mappings
         public string SetStateTo { get; set; }
 
         /// <summary>
-        /// The request.
+        /// The request model.
         /// </summary>
         public RequestModel Request { get; set; }
 
         /// <summary>
-        /// The response.
+        /// The response model.
         /// </summary>
         public ResponseModel Response { get; set; }
+
+        /// <summary>
+        /// Saves this mapping as a static mapping file.
+        /// </summary>
+        public bool? SaveToFile { get; set; }
     }
 }
\ No newline at end of file
diff --git a/src/WireMock.Net/Admin/Mappings/ResponseModel.cs b/src/WireMock.Net/Admin/Mappings/ResponseModel.cs
index 5998d4e8..29c71b44 100644
--- a/src/WireMock.Net/Admin/Mappings/ResponseModel.cs
+++ b/src/WireMock.Net/Admin/Mappings/ResponseModel.cs
@@ -58,9 +58,9 @@ namespace WireMock.Admin.Mappings
         public EncodingModel BodyEncoding { get; set; }
 
         /// <summary>
-        /// Gets or sets a value indicating whether [use transformer].
+        /// Use Handlebars transformer.
         /// </summary>
-        public bool UseTransformer { get; set; }
+        public bool? UseTransformer { get; set; }
 
         /// <summary>
         /// Gets or sets the headers.
diff --git a/src/WireMock.Net/IMapping.cs b/src/WireMock.Net/IMapping.cs
index 4dca9571..3d3beefa 100644
--- a/src/WireMock.Net/IMapping.cs
+++ b/src/WireMock.Net/IMapping.cs
@@ -1,6 +1,7 @@
-using System;
+using JetBrains.Annotations;
+using System;
 using System.Threading.Tasks;
-using JetBrains.Annotations;
+using WireMock.Handlers;
 using WireMock.Matchers.Request;
 using WireMock.ResponseProviders;
 
@@ -60,6 +61,11 @@ namespace WireMock
         /// </summary>
         IResponseProvider Provider { get; }
 
+        /// <summary>
+        /// The FileSystemHandler.
+        /// </summary>
+        IFileSystemHandler FileSystemHandler { get; }
+
         /// <summary>
         /// Is State started ?
         /// </summary>
diff --git a/src/WireMock.Net/Mapping.cs b/src/WireMock.Net/Mapping.cs
index cbf24ec5..dd4d818b 100644
--- a/src/WireMock.Net/Mapping.cs
+++ b/src/WireMock.Net/Mapping.cs
@@ -1,6 +1,7 @@
-using System;
+using JetBrains.Annotations;
+using System;
 using System.Threading.Tasks;
-using JetBrains.Annotations;
+using WireMock.Handlers;
 using WireMock.Matchers.Request;
 using WireMock.ResponseProviders;
 
@@ -38,6 +39,9 @@ namespace WireMock
         /// <inheritdoc cref="IMapping.Provider" />
         public IResponseProvider Provider { get; }
 
+        /// <inheritdoc cref="IMapping.FileSystemHandler" />
+        public IFileSystemHandler FileSystemHandler { get; }
+
         /// <inheritdoc cref="IMapping.IsStartState" />
         public bool IsStartState => Scenario == null || Scenario != null && NextState != null && ExecutionConditionState == null;
 
@@ -50,17 +54,21 @@ namespace WireMock
         /// <param name="guid">The unique identifier.</param>
         /// <param name="title">The unique title (can be null).</param>
         /// <param name="path">The full file path from this mapping title (can be null).</param>
+        /// <param name="fileSystemHandler">The fileSystemHandler.</param>
         /// <param name="requestMatcher">The request matcher.</param>
         /// <param name="provider">The provider.</param>
         /// <param name="priority">The priority for this mapping.</param>
         /// <param name="scenario">The scenario. [Optional]</param>
         /// <param name="executionConditionState">State in which the current mapping can occur. [Optional]</param>
         /// <param name="nextState">The next state which will occur after the current mapping execution. [Optional]</param>
-        public Mapping(Guid guid, [CanBeNull] string title, [CanBeNull] string path, IRequestMatcher requestMatcher, IResponseProvider provider, int priority, [CanBeNull] string scenario, [CanBeNull] string executionConditionState, [CanBeNull] string nextState)
+        public Mapping(Guid guid, [CanBeNull] string title, [CanBeNull] string path,
+            [NotNull] IFileSystemHandler fileSystemHandler, [NotNull] IRequestMatcher requestMatcher, [NotNull] IResponseProvider provider,
+            int priority, [CanBeNull] string scenario, [CanBeNull] string executionConditionState, [CanBeNull] string nextState)
         {
             Guid = guid;
             Title = title;
             Path = path;
+            FileSystemHandler = fileSystemHandler;
             RequestMatcher = requestMatcher;
             Provider = provider;
             Priority = priority;
@@ -72,7 +80,7 @@ namespace WireMock
         /// <inheritdoc cref="IMapping.ResponseToAsync" />
         public async Task<ResponseMessage> ResponseToAsync(RequestMessage requestMessage)
         {
-            return await Provider.ProvideResponseAsync(requestMessage);
+            return await Provider.ProvideResponseAsync(requestMessage, FileSystemHandler);
         }
 
         /// <inheritdoc cref="IMapping.GetRequestMatchResult" />
diff --git a/src/WireMock.Net/MappingRegistrationCallback.cs b/src/WireMock.Net/MappingRegistrationCallback.cs
index cd5ad6f3..0a78d11a 100644
--- a/src/WireMock.Net/MappingRegistrationCallback.cs
+++ b/src/WireMock.Net/MappingRegistrationCallback.cs
@@ -4,5 +4,6 @@
     /// The registration callback.
     /// </summary>
     /// <param name="mapping">The mapping.</param>
-    public delegate void RegistrationCallback(IMapping mapping);
+    /// <param name="saveToFile">Optional boolean to indicate if this mapping should be saved as static mapping file.</param>
+    public delegate void RegistrationCallback(IMapping mapping, bool saveToFile = false);
 }
\ No newline at end of file
diff --git a/src/WireMock.Net/ResponseBuilders/Response.cs b/src/WireMock.Net/ResponseBuilders/Response.cs
index 6e2fd7cf..f806ee84 100644
--- a/src/WireMock.Net/ResponseBuilders/Response.cs
+++ b/src/WireMock.Net/ResponseBuilders/Response.cs
@@ -21,8 +21,6 @@ namespace WireMock.ResponseBuilders
     /// </summary>
     public class Response : IResponseBuilder
     {
-        private readonly IFileSystemHandler _fileSystemHandler;
-        private readonly ResponseMessageTransformer _responseMessageTransformer;
         private HttpClient _httpClientForProxy;
 
         /// <summary>
@@ -94,9 +92,6 @@ namespace WireMock.ResponseBuilders
         private Response(ResponseMessage responseMessage)
         {
             ResponseMessage = responseMessage;
-
-            _fileSystemHandler = new LocalFileSystemHandler();
-            _responseMessageTransformer = new ResponseMessageTransformer(_fileSystemHandler);
         }
 
         /// <summary>
@@ -225,18 +220,17 @@ namespace WireMock.ResponseBuilders
 
             ResponseMessage.BodyData = new BodyData
             {
-                BodyAsFileIsCached = cache
+                BodyAsFileIsCached = cache,
+                BodyAsFile = filename
             };
 
             if (cache && !UseTransformer)
             {
                 ResponseMessage.BodyData.DetectedBodyType = BodyType.Bytes;
-                ResponseMessage.BodyData.BodyAsBytes = _fileSystemHandler.ReadResponseBodyAsFile(filename);
             }
             else
             {
                 ResponseMessage.BodyData.DetectedBodyType = BodyType.File;
-                ResponseMessage.BodyData.BodyAsFile = filename;
             }
 
             return this;
@@ -377,12 +371,7 @@ namespace WireMock.ResponseBuilders
             return this;
         }
 
-        /// <summary>
-        /// The provide response.
-        /// </summary>
-        /// <param name="requestMessage">The request.</param>
-        /// <returns>The <see cref="ResponseMessage"/>.</returns>
-        public async Task<ResponseMessage> ProvideResponseAsync(RequestMessage requestMessage)
+        public async Task<ResponseMessage> ProvideResponseAsync(RequestMessage requestMessage, IFileSystemHandler fileSystemHandler)
         {
             Check.NotNull(requestMessage, nameof(requestMessage));
 
@@ -421,10 +410,16 @@ namespace WireMock.ResponseBuilders
 
             if (UseTransformer)
             {
-                return _responseMessageTransformer.Transform(requestMessage, ResponseMessage);
+                var responseMessageTransformer = new ResponseMessageTransformer(fileSystemHandler);
+                return responseMessageTransformer.Transform(requestMessage, ResponseMessage);
+            }
+
+            if (!UseTransformer && ResponseMessage.BodyData?.BodyAsFileIsCached == true)
+            {
+                ResponseMessage.BodyData.BodyAsBytes = fileSystemHandler.ReadResponseBodyAsFile(ResponseMessage.BodyData.BodyAsFile);
+                ResponseMessage.BodyData.BodyAsFile = null;
             }
 
-            // Just return normal defined ResponseMessage
             return ResponseMessage;
         }
     }
diff --git a/src/WireMock.Net/ResponseMessageBuilder.cs b/src/WireMock.Net/ResponseMessageBuilder.cs
index a6d85bb5..1e213976 100644
--- a/src/WireMock.Net/ResponseMessageBuilder.cs
+++ b/src/WireMock.Net/ResponseMessageBuilder.cs
@@ -27,7 +27,11 @@ namespace WireMock
                 response.BodyData = new BodyData
                 {
                     DetectedBodyType = BodyType.Json,
-                    BodyAsJson = new StatusModel { Status = message, Guid = guid }
+                    BodyAsJson = new StatusModel
+                    {
+                        Guid = guid,
+                        Status = message
+                    }
                 };
             }
 
diff --git a/src/WireMock.Net/ResponseProviders/DynamicAsyncResponseProvider.cs b/src/WireMock.Net/ResponseProviders/DynamicAsyncResponseProvider.cs
index afbaa664..f1456b31 100644
--- a/src/WireMock.Net/ResponseProviders/DynamicAsyncResponseProvider.cs
+++ b/src/WireMock.Net/ResponseProviders/DynamicAsyncResponseProvider.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Threading.Tasks;
-using JetBrains.Annotations;
-using WireMock.Validation;
+using WireMock.Handlers;
 
 namespace WireMock.ResponseProviders
 {
@@ -9,14 +8,12 @@ namespace WireMock.ResponseProviders
     {
         private readonly Func<RequestMessage, Task<ResponseMessage>> _responseMessageFunc;
 
-        public DynamicAsyncResponseProvider([NotNull] Func<RequestMessage, Task<ResponseMessage>> responseMessageFunc)
+        public DynamicAsyncResponseProvider(Func<RequestMessage, Task<ResponseMessage>> responseMessageFunc)
         {
-            Check.NotNull(responseMessageFunc, nameof(responseMessageFunc));
-
             _responseMessageFunc = responseMessageFunc;
         }
 
-        public Task<ResponseMessage> ProvideResponseAsync(RequestMessage requestMessage)
+        public Task<ResponseMessage> ProvideResponseAsync(RequestMessage requestMessage, IFileSystemHandler fileSystemHandler)
         {
             return _responseMessageFunc(requestMessage);
         }
diff --git a/src/WireMock.Net/ResponseProviders/DynamicResponseProvider.cs b/src/WireMock.Net/ResponseProviders/DynamicResponseProvider.cs
index d04b9fe5..534f7a5e 100644
--- a/src/WireMock.Net/ResponseProviders/DynamicResponseProvider.cs
+++ b/src/WireMock.Net/ResponseProviders/DynamicResponseProvider.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Threading.Tasks;
-using JetBrains.Annotations;
-using WireMock.Validation;
+using WireMock.Handlers;
 
 namespace WireMock.ResponseProviders
 {
@@ -9,14 +8,12 @@ namespace WireMock.ResponseProviders
     {
         private readonly Func<RequestMessage, ResponseMessage> _responseMessageFunc;
 
-        public DynamicResponseProvider([NotNull] Func<RequestMessage, ResponseMessage> responseMessageFunc)
+        public DynamicResponseProvider(Func<RequestMessage, ResponseMessage> responseMessageFunc)
         {
-            Check.NotNull(responseMessageFunc, nameof(responseMessageFunc));
-
             _responseMessageFunc = responseMessageFunc;
         }
 
-        public Task<ResponseMessage> ProvideResponseAsync(RequestMessage requestMessage)
+        public Task<ResponseMessage> ProvideResponseAsync(RequestMessage requestMessage, IFileSystemHandler fileSystemHandler)
         {
             return Task.FromResult(_responseMessageFunc(requestMessage));
         }
diff --git a/src/WireMock.Net/ResponseProviders/IResponseProvider.cs b/src/WireMock.Net/ResponseProviders/IResponseProvider.cs
index 38271f7d..ca4f65d4 100644
--- a/src/WireMock.Net/ResponseProviders/IResponseProvider.cs
+++ b/src/WireMock.Net/ResponseProviders/IResponseProvider.cs
@@ -1,5 +1,6 @@
 using System.Threading.Tasks;
 using JetBrains.Annotations;
+using WireMock.Handlers;
 
 namespace WireMock.ResponseProviders
 {
@@ -12,7 +13,8 @@ namespace WireMock.ResponseProviders
         /// The provide response.
         /// </summary>
         /// <param name="requestMessage">The request.</param>
+        /// <param name="fileSystemHandler">The fileSystemHandler.</param>
         /// <returns>The <see cref="ResponseMessage"/>.</returns>
-        Task<ResponseMessage> ProvideResponseAsync([NotNull] RequestMessage requestMessage);
+        Task<ResponseMessage> ProvideResponseAsync([NotNull] RequestMessage requestMessage, [NotNull] IFileSystemHandler fileSystemHandler);
     }
 }
\ No newline at end of file
diff --git a/src/WireMock.Net/ResponseProviders/ProxyAsyncResponseProvider.cs b/src/WireMock.Net/ResponseProviders/ProxyAsyncResponseProvider.cs
index f1283138..748a0822 100644
--- a/src/WireMock.Net/ResponseProviders/ProxyAsyncResponseProvider.cs
+++ b/src/WireMock.Net/ResponseProviders/ProxyAsyncResponseProvider.cs
@@ -1,26 +1,22 @@
 using System;
 using System.Threading.Tasks;
-using JetBrains.Annotations;
+using WireMock.Handlers;
 using WireMock.Settings;
-using WireMock.Validation;
 
 namespace WireMock.ResponseProviders
 {
     internal class ProxyAsyncResponseProvider : IResponseProvider
     {
-        private readonly Func<RequestMessage, IProxyAndRecordSettings, Task<ResponseMessage>> _responseMessageFunc;
-        private readonly IProxyAndRecordSettings _settings;
+        private readonly Func<RequestMessage, IFluentMockServerSettings, Task<ResponseMessage>> _responseMessageFunc;
+        private readonly IFluentMockServerSettings _settings;
 
-        public ProxyAsyncResponseProvider([NotNull] Func<RequestMessage, IProxyAndRecordSettings, Task<ResponseMessage>> responseMessageFunc, [NotNull] IProxyAndRecordSettings settings)
+        public ProxyAsyncResponseProvider(Func<RequestMessage, IFluentMockServerSettings, Task<ResponseMessage>> responseMessageFunc, IFluentMockServerSettings settings)
         {
-            Check.NotNull(responseMessageFunc, nameof(responseMessageFunc));
-            Check.NotNull(settings, nameof(settings));
-
             _responseMessageFunc = responseMessageFunc;
             _settings = settings;
         }
 
-        public Task<ResponseMessage> ProvideResponseAsync(RequestMessage requestMessage)
+        public Task<ResponseMessage> ProvideResponseAsync(RequestMessage requestMessage, IFileSystemHandler fileSystemHandler)
         {
             return _responseMessageFunc(requestMessage, _settings);
         }
diff --git a/src/WireMock.Net/Serialization/MappingConverter.cs b/src/WireMock.Net/Serialization/MappingConverter.cs
index 5f848b48..0a8f9010 100644
--- a/src/WireMock.Net/Serialization/MappingConverter.cs
+++ b/src/WireMock.Net/Serialization/MappingConverter.cs
@@ -28,7 +28,7 @@ namespace WireMock.Serialization
             {
                 Guid = mapping.Guid,
                 Title = mapping.Title,
-                Priority = mapping.Priority,
+                Priority = mapping.Priority != 0 ? mapping.Priority : (int?) null,
                 Scenario = mapping.Scenario,
                 WhenStateIs = mapping.ExecutionConditionState,
                 SetStateTo = mapping.NextState,
@@ -66,7 +66,7 @@ namespace WireMock.Serialization
                     Params = paramsMatchers != null && paramsMatchers.Any() ? paramsMatchers.Select(pm => new ParamModel
                     {
                         Name = pm.Key,
-                        IgnoreCase = pm.IgnoreCase,
+                        IgnoreCase = pm.IgnoreCase == true ? true : (bool?) null,
                         Matchers = MatcherMapper.Map(pm.Matchers)
                     }).ToList() : null,
 
@@ -92,7 +92,7 @@ namespace WireMock.Serialization
                 mappingModel.Response.BodyAsBytes = null;
                 mappingModel.Response.BodyAsFile = null;
                 mappingModel.Response.BodyAsFileIsCached = null;
-                mappingModel.Response.UseTransformer = false;
+                mappingModel.Response.UseTransformer = null;
                 mappingModel.Response.BodyEncoding = null;
                 mappingModel.Response.ProxyUrl = response.ProxyUrl;
             }
@@ -101,7 +101,10 @@ namespace WireMock.Serialization
                 mappingModel.Response.BodyDestination = response.ResponseMessage.BodyDestination;
                 mappingModel.Response.StatusCode = response.ResponseMessage.StatusCode;
                 mappingModel.Response.Headers = Map(response.ResponseMessage.Headers);
-                mappingModel.Response.UseTransformer = response.UseTransformer;
+                if (response.UseTransformer)
+                {
+                    mappingModel.Response.UseTransformer = response.UseTransformer;
+                }
 
                 if (response.ResponseMessage.BodyData != null)
                 {
@@ -113,7 +116,10 @@ namespace WireMock.Serialization
 
                         case BodyType.Json:
                             mappingModel.Response.BodyAsJson = response.ResponseMessage.BodyData.BodyAsJson;
-                            mappingModel.Response.BodyAsJsonIndented = response.ResponseMessage.BodyData.BodyAsJsonIndented;
+                            if (response.ResponseMessage.BodyData.BodyAsJsonIndented == true)
+                            {
+                                mappingModel.Response.BodyAsJsonIndented = response.ResponseMessage.BodyData.BodyAsJsonIndented;
+                            }
                             break;
 
                         case BodyType.Bytes:
diff --git a/src/WireMock.Net/Server/FluentMockServer.Admin.cs b/src/WireMock.Net/Server/FluentMockServer.Admin.cs
index 1da20c3c..971c655b 100644
--- a/src/WireMock.Net/Server/FluentMockServer.Admin.cs
+++ b/src/WireMock.Net/Server/FluentMockServer.Admin.cs
@@ -43,7 +43,7 @@ namespace WireMock.Server
         private readonly RegexMatcher _adminMappingsGuidPathMatcher = new RegexMatcher(MatchBehaviour.AcceptOnMatch, @"^\/__admin\/mappings\/([0-9A-Fa-f]{8}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{12})$");
         private readonly RegexMatcher _adminRequestsGuidPathMatcher = new RegexMatcher(MatchBehaviour.AcceptOnMatch, @"^\/__admin\/requests\/([0-9A-Fa-f]{8}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{12})$");
 
-        private readonly JsonSerializerSettings _settings = new JsonSerializerSettings
+        private readonly JsonSerializerSettings _jsonSerializerSettings = new JsonSerializerSettings
         {
             Formatting = Formatting.Indented,
             NullValueHandling = NullValueHandling.Ignore
@@ -242,23 +242,23 @@ namespace WireMock.Server
                 respondProvider.AtPriority(ProxyPriority);
             }
 
-            respondProvider.RespondWith(new ProxyAsyncResponseProvider(ProxyAndRecordAsync, settings.ProxyAndRecordSettings));
+            respondProvider.RespondWith(new ProxyAsyncResponseProvider(ProxyAndRecordAsync, settings));
         }
 
-        private async Task<ResponseMessage> ProxyAndRecordAsync(RequestMessage requestMessage, IProxyAndRecordSettings settings)
+        private async Task<ResponseMessage> ProxyAndRecordAsync(RequestMessage requestMessage, IFluentMockServerSettings settings)
         {
             var requestUri = new Uri(requestMessage.Url);
-            var proxyUri = new Uri(settings.Url);
+            var proxyUri = new Uri(settings.ProxyAndRecordSettings.Url);
             var proxyUriWithRequestPathAndQuery = new Uri(proxyUri, requestUri.PathAndQuery);
 
             var responseMessage = await HttpClientHelper.SendAsync(_httpClientForProxy, requestMessage, proxyUriWithRequestPathAndQuery.AbsoluteUri);
 
-            if (settings.SaveMapping)
+            if (settings.ProxyAndRecordSettings.SaveMapping)
             {
-                var mapping = ToMapping(requestMessage, responseMessage, settings.BlackListedHeaders ?? new string[] { });
+                var mapping = ToMapping(requestMessage, responseMessage, settings.ProxyAndRecordSettings.BlackListedHeaders ?? new string[] { });
                 _options.Mappings.TryAdd(mapping.Guid, mapping);
 
-                if (settings.SaveMappingToFile)
+                if (settings.ProxyAndRecordSettings.SaveMappingToFile)
                 {
                     SaveMappingToFile(mapping);
                 }
@@ -302,7 +302,7 @@ namespace WireMock.Server
 
             var response = Response.Create(responseMessage);
 
-            return new Mapping(Guid.NewGuid(), string.Empty, null, request, response, 0, null, null, null);
+            return new Mapping(Guid.NewGuid(), string.Empty, null, _fileSystemHandler, request, response, 0, null, null, null);
         }
         #endregion
 
@@ -407,7 +407,7 @@ namespace WireMock.Server
 
             _logger.Info("Saving Mapping file {0}", filename);
 
-            _fileSystemHandler.WriteMappingFile(path, JsonConvert.SerializeObject(model, _settings));
+            _fileSystemHandler.WriteMappingFile(path, JsonConvert.SerializeObject(model, _jsonSerializerSettings));
         }
 
         private static string SanitizeFileName(string name, char replaceChar = '_')
@@ -471,7 +471,7 @@ namespace WireMock.Server
 
             var responseBuilder = InitResponseBuilder(mappingModel.Response);
 
-            var respondProvider = Given(requestBuilder);
+            var respondProvider = Given(requestBuilder, mappingModel.SaveToFile == true);
 
             if (guid != null)
             {
@@ -722,7 +722,7 @@ namespace WireMock.Server
                 responseBuilder = responseBuilder.WithDelay(responseModel.Delay.Value);
             }
 
-            if (responseModel.UseTransformer)
+            if (responseModel.UseTransformer == true)
             {
                 responseBuilder = responseBuilder.WithTransformer();
             }
@@ -793,7 +793,7 @@ namespace WireMock.Server
                 BodyData = new BodyData
                 {
                     DetectedBodyType = BodyType.String,
-                    BodyAsString = JsonConvert.SerializeObject(result, keepNullValues ? _settingsIncludeNullValues : _settings)
+                    BodyAsString = JsonConvert.SerializeObject(result, keepNullValues ? _settingsIncludeNullValues : _jsonSerializerSettings)
                 },
                 StatusCode = 200,
                 Headers = new Dictionary<string, WireMockList<string>> { { HttpKnownHeaderNames.ContentType, new WireMockList<string>(ContentTypeJson) } }
diff --git a/src/WireMock.Net/Server/FluentMockServer.cs b/src/WireMock.Net/Server/FluentMockServer.cs
index 6ac06198..c9ba2d92 100644
--- a/src/WireMock.Net/Server/FluentMockServer.cs
+++ b/src/WireMock.Net/Server/FluentMockServer.cs
@@ -203,7 +203,7 @@ namespace WireMock.Server
                 Urls = new[] { $"{(settings.UseSSL == true ? "https" : "http")}://localhost:{port}" };
             }
 
-            _options.FileSystemHandler = settings.FileSystemHandler;
+            _options.FileSystemHandler = _fileSystemHandler;
             _options.PreWireMockMiddlewareInit = settings.PreWireMockMiddlewareInit;
             _options.PostWireMockMiddlewareInit = settings.PostWireMockMiddlewareInit;
             _options.Logger = _logger;
@@ -430,14 +430,15 @@ namespace WireMock.Server
         /// The given.
         /// </summary>
         /// <param name="requestMatcher">The request matcher.</param>
+        /// <param name="saveToFile">Optional boolean to indicate if this mapping should be saved as static mapping file.</param>
         /// <returns>The <see cref="IRespondWithAProvider"/>.</returns>
         [PublicAPI]
-        public IRespondWithAProvider Given(IRequestMatcher requestMatcher)
+        public IRespondWithAProvider Given(IRequestMatcher requestMatcher, bool saveToFile = false)
         {
-            return new RespondWithAProvider(RegisterMapping, requestMatcher);
+            return new RespondWithAProvider(RegisterMapping, requestMatcher, _fileSystemHandler, saveToFile);
         }
 
-        private void RegisterMapping(IMapping mapping)
+        private void RegisterMapping(IMapping mapping, bool saveToFile)
         {
             // Check a mapping exists with the same Guid, if so, replace it.
             if (_options.Mappings.ContainsKey(mapping.Guid))
@@ -448,6 +449,11 @@ namespace WireMock.Server
             {
                 _options.Mappings.TryAdd(mapping.Guid, mapping);
             }
+
+            if (saveToFile)
+            {
+                SaveMappingToFile(mapping);
+            }
         }
     }
 }
\ No newline at end of file
diff --git a/src/WireMock.Net/Server/RespondWithAProvider.cs b/src/WireMock.Net/Server/RespondWithAProvider.cs
index b4325d69..1db7db6b 100644
--- a/src/WireMock.Net/Server/RespondWithAProvider.cs
+++ b/src/WireMock.Net/Server/RespondWithAProvider.cs
@@ -1,4 +1,5 @@
 using System;
+using WireMock.Handlers;
 using WireMock.Matchers.Request;
 using WireMock.ResponseProviders;
 
@@ -17,6 +18,8 @@ namespace WireMock.Server
         private string _scenario;
         private readonly RegistrationCallback _registrationCallback;
         private readonly IRequestMatcher _requestMatcher;
+        private readonly IFileSystemHandler _fileSystemHandler;
+        private readonly bool _saveToFile;
 
         public Guid Guid { get; private set; } = Guid.NewGuid();
 
@@ -25,10 +28,14 @@ namespace WireMock.Server
         /// </summary>
         /// <param name="registrationCallback">The registration callback.</param>
         /// <param name="requestMatcher">The request matcher.</param>
-        public RespondWithAProvider(RegistrationCallback registrationCallback, IRequestMatcher requestMatcher)
+        /// <param name="fileSystemHandler">The fileSystemHandler.</param>
+        /// <param name="saveToFile">Optional boolean to indicate if this mapping should be saved as static mapping file.</param>
+        public RespondWithAProvider(RegistrationCallback registrationCallback, IRequestMatcher requestMatcher, IFileSystemHandler fileSystemHandler, bool saveToFile = false)
         {
             _registrationCallback = registrationCallback;
             _requestMatcher = requestMatcher;
+            _fileSystemHandler = fileSystemHandler;
+            _saveToFile = saveToFile;
         }
 
         /// <summary>
@@ -37,7 +44,7 @@ namespace WireMock.Server
         /// <param name="provider">The provider.</param>
         public void RespondWith(IResponseProvider provider)
         {
-            _registrationCallback(new Mapping(Guid, _title, _path, _requestMatcher, provider, _priority, _scenario, _executionConditionState, _nextState));
+            _registrationCallback(new Mapping(Guid, _title, _path, _fileSystemHandler, _requestMatcher, provider, _priority, _scenario, _executionConditionState, _nextState), _saveToFile);
         }
 
         /// <see cref="IRespondWithAProvider.WithGuid(string)"/>
diff --git a/src/WireMock.Net/Settings/FluentMockServerSettings.cs b/src/WireMock.Net/Settings/FluentMockServerSettings.cs
index 9859ae58..ab02e13d 100644
--- a/src/WireMock.Net/Settings/FluentMockServerSettings.cs
+++ b/src/WireMock.Net/Settings/FluentMockServerSettings.cs
@@ -82,6 +82,6 @@ namespace WireMock.Settings
         /// <inheritdoc cref="IFluentMockServerSettings.FileSystemHandler"/>
         [PublicAPI]
         [JsonIgnore]
-        public IFileSystemHandler FileSystemHandler { get; set; } = new LocalFileSystemHandler();
+        public IFileSystemHandler FileSystemHandler { get; set; }
     }
 }
\ No newline at end of file
diff --git a/test/WireMock.Net.Tests/FluentMockServerTests.Admin.cs b/test/WireMock.Net.Tests/FluentMockServerTests.Admin.cs
index 471d1b85..06b6a30a 100644
--- a/test/WireMock.Net.Tests/FluentMockServerTests.Admin.cs
+++ b/test/WireMock.Net.Tests/FluentMockServerTests.Admin.cs
@@ -375,5 +375,32 @@ namespace WireMock.Net.Tests
             fileMock.Verify(f => f.GetMappingFolder(), Times.Once);
             fileMock.Verify(f => f.FolderExists(It.IsAny<string>()), Times.Once);
         }
+
+        [Fact]
+        public void FluentMockServer_Admin_AddMappingsAndSaveToFile()
+        {
+            // Assign
+            string guid = "791a3f31-6946-aaaa-8e6f-0237c7442222";
+            var staticMappingHandlerMock = new Mock<IFileSystemHandler>();
+            staticMappingHandlerMock.Setup(m => m.GetMappingFolder()).Returns("folder");
+            staticMappingHandlerMock.Setup(m => m.FolderExists(It.IsAny<string>())).Returns(true);
+            staticMappingHandlerMock.Setup(m => m.WriteMappingFile(It.IsAny<string>(), It.IsAny<string>()));
+
+            var server = FluentMockServer.Start(new FluentMockServerSettings
+            {
+                FileSystemHandler = staticMappingHandlerMock.Object
+            });
+
+            // Act
+            server
+                .Given(Request.Create().WithPath($"/foo_{Guid.NewGuid()}"), true)
+                .WithGuid(guid)
+                .RespondWith(Response.Create().WithBody("post and save test"));
+
+            // Assert and Verify
+            staticMappingHandlerMock.Verify(m => m.GetMappingFolder(), Times.Once);
+            staticMappingHandlerMock.Verify(m => m.FolderExists("folder"), Times.Once);
+            staticMappingHandlerMock.Verify(m => m.WriteMappingFile(Path.Combine("folder", guid + ".json"), It.IsAny<string>()), Times.Once);
+        }
     }
 }
\ No newline at end of file
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseCreateTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseCreateTests.cs
index 54bbbc69..aa0d0eb0 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseCreateTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseCreateTests.cs
@@ -1,5 +1,7 @@
 using System.Threading.Tasks;
+using Moq;
 using NFluent;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using Xunit;
@@ -8,6 +10,8 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseCreateTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
+
         [Fact]
         public async Task Response_Create_Func()
         {
@@ -18,7 +22,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create(() => responseMessage);
 
             // Act
-            var providedResponse = await response.ProvideResponseAsync(request);
+            var providedResponse = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(providedResponse).Equals(responseMessage);
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithBodyTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithBodyTests.cs
index 4328fd4c..2080c515 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithBodyTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithBodyTests.cs
@@ -1,17 +1,20 @@
-using System;
+using Moq;
+using Newtonsoft.Json.Linq;
+using NFluent;
+using System;
 using System.Text;
 using System.Threading.Tasks;
-using NFluent;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using WireMock.Util;
 using Xunit;
-using Newtonsoft.Json.Linq;
 
 namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithBodyTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
         private const string ClientIp = "::1";
 
         [Fact]
@@ -28,7 +31,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithBody(new byte[] { 48, 49 }, BodyDestinationFormat.String, Encoding.ASCII);
 
             // act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // then
             Check.That(responseMessage.BodyData.BodyAsString).Equals("01");
@@ -50,7 +53,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithBody(new byte[] { 48, 49 }, BodyDestinationFormat.SameAsSource, Encoding.ASCII);
 
             // act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // then
             Check.That(responseMessage.BodyData.BodyAsBytes).ContainsExactly(new byte[] { 48, 49 });
@@ -72,7 +75,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithBody("test", null, Encoding.ASCII);
 
             // act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // then
             Check.That(responseMessage.BodyData.BodyAsString).Equals("test");
@@ -94,7 +97,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithBodyAsJson(x, Encoding.ASCII);
 
             // act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // then
             Check.That(responseMessage.BodyData.BodyAsJson).Equals(x);
@@ -116,7 +119,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithBodyAsJson(x, true);
 
             // act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // then
             Check.That(responseMessage.BodyData.BodyAsJson).Equals(x);
@@ -132,7 +135,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithBody("r", BodyDestinationFormat.SameAsSource, Encoding.ASCII);
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsBytes).IsNull();
@@ -150,7 +153,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithBody("r", BodyDestinationFormat.Bytes, Encoding.ASCII);
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).IsNull();
@@ -168,7 +171,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithBody("{ \"value\": 42 }", BodyDestinationFormat.Json, Encoding.ASCII);
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).IsNull();
@@ -190,7 +193,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithBody(req => $"path: {req.Path}");
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).IsEqualTo("path: /test");
@@ -201,7 +204,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             Check.That(responseMessage.Headers["H1"].ToString()).IsEqualTo("X1");
             Check.That(responseMessage.Headers["H2"].ToString()).IsEqualTo("X2");
         }
-        
+
         [Fact]
         public async Task Response_ProvideResponse_WithJsonBodyAndTransform_Func()
         {
@@ -211,15 +214,15 @@ namespace WireMock.Net.Tests.ResponseBuilders
 
             var request1 = new RequestMessage(new UrlDetails($"http://localhost/test?id={request1Id}"), "GET", ClientIp);
             var request2 = new RequestMessage(new UrlDetails($"http://localhost/test?id={request2Id}"), "GET", ClientIp);
-            
+
             var response = Response.Create()
                 .WithStatusCode(200)
                 .WithBodyAsJson(JObject.Parse("{ \"id\": \"{{request.query.id}}\" }"))
                 .WithTransformer();
 
             // Act
-            var response1Message = await response.ProvideResponseAsync(request1);
-            var response2Message = await response.ProvideResponseAsync(request2);
+            var response1Message = await response.ProvideResponseAsync(request1, _fileSystemHandlerMock.Object);
+            var response2Message = await response.ProvideResponseAsync(request2, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(((JToken)response1Message.BodyData.BodyAsJson).SelectToken("id")?.Value<int>()).IsEqualTo(request1Id);
@@ -237,13 +240,13 @@ namespace WireMock.Net.Tests.ResponseBuilders
         public async Task Response_ProvideResponse_WithBodyAsFile()
         {
             var fileContents = "testFileContents" + Guid.NewGuid();
-            var bodyDataAsFile = new BodyData {BodyAsFile = fileContents};
+            var bodyDataAsFile = new BodyData { BodyAsFile = fileContents };
 
             var request1 = new RequestMessage(new UrlDetails("http://localhost/__admin/files/filename.txt"), "PUT", ClientIp, bodyDataAsFile);
 
             var response = Response.Create().WithStatusCode(200).WithBody(fileContents);
 
-            var provideResponseAsync = await response.ProvideResponseAsync(request1);
+            var provideResponseAsync = await response.ProvideResponseAsync(request1, _fileSystemHandlerMock.Object);
 
             Check.That(provideResponseAsync.StatusCode).IsEqualTo(200);
             Check.That(provideResponseAsync.BodyData.BodyAsString).Contains(fileContents);
@@ -259,7 +262,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
 
             var response = Response.Create().WithStatusCode(200).WithBody(fileContents);
 
-            var provideResponseAsync = await response.ProvideResponseAsync(request1);
+            var provideResponseAsync = await response.ProvideResponseAsync(request1, _fileSystemHandlerMock.Object);
 
             Check.That(provideResponseAsync.StatusCode).IsEqualTo(200);
             Check.That(provideResponseAsync.BodyData.BodyAsString).Contains(fileContents);
@@ -275,7 +278,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
 
             var response = Response.Create().WithStatusCode(200).WithBody("File deleted.");
 
-            var provideResponseAsync = await response.ProvideResponseAsync(request1);
+            var provideResponseAsync = await response.ProvideResponseAsync(request1, _fileSystemHandlerMock.Object);
 
             Check.That(provideResponseAsync.StatusCode).IsEqualTo(200);
             Check.That(provideResponseAsync.BodyData.BodyAsString).Contains("File deleted.");
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithCallbackTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithCallbackTests.cs
index 910717c3..76912fbc 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithCallbackTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithCallbackTests.cs
@@ -1,5 +1,7 @@
-using System.Threading.Tasks;
+using Moq;
 using NFluent;
+using System.Threading.Tasks;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using WireMock.Util;
@@ -9,6 +11,8 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithCallbackTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
+
         [Fact]
         public async Task Response_WithCallback()
         {
@@ -17,7 +21,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithCallback(req => new ResponseMessage { BodyData = new BodyData { DetectedBodyType = BodyType.String, BodyAsString = req.Path + "Bar" }, StatusCode = 302 });
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).IsEqualTo("/fooBar");
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsFileTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsFileTests.cs
index 27eff07b..05f387d1 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsFileTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsFileTests.cs
@@ -6,7 +6,6 @@ using System.Threading.Tasks;
 using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
-using WireMock.Transformers;
 using Xunit;
 
 namespace WireMock.Net.Tests.ResponseBuilders
@@ -35,11 +34,8 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 })
                 .WithTransformer();
 
-            response.SetPrivateFieldValue("_fileSystemHandler", _filesystemHandlerMock.Object);
-            response.SetPrivateFieldValue("_responseMessageTransformer", new ResponseMessageTransformer(_filesystemHandlerMock.Object));
-
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _filesystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -63,11 +59,8 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 })
                 .WithTransformer();
 
-            response.SetPrivateFieldValue("_fileSystemHandler", _filesystemHandlerMock.Object);
-            response.SetPrivateFieldValue("_responseMessageTransformer", new ResponseMessageTransformer(_filesystemHandlerMock.Object));
-
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _filesystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -92,7 +85,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request)).Throws<ArgumentOutOfRangeException>();
+            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request, _filesystemHandlerMock.Object)).Throws<ArgumentOutOfRangeException>();
 
             // Verify
             _filesystemHandlerMock.Verify(fs => fs.ReadResponseBodyAsString(It.IsAny<string>()), Times.Never);
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsJsonPathTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsJsonPathTests.cs
index 88809e1d..f0bda9aa 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsJsonPathTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsJsonPathTests.cs
@@ -1,7 +1,9 @@
 using System;
 using System.Threading.Tasks;
+using Moq;
 using Newtonsoft.Json.Linq;
 using NFluent;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using WireMock.Util;
@@ -11,6 +13,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithHandlebarsJsonPathTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
         private const string ClientIp = "::1";
 
         [Fact]
@@ -60,7 +63,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -86,7 +89,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -140,7 +143,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals($"{{{Environment.NewLine}  \"Name\": \"Acme Co\",{Environment.NewLine}  \"Products\": [{Environment.NewLine}    {{{Environment.NewLine}      \"Name\": \"Anvil\",{Environment.NewLine}      \"Price\": 50{Environment.NewLine}    }}{Environment.NewLine}  ]{Environment.NewLine}}}");
@@ -193,7 +196,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals($"{{{Environment.NewLine}  \"Name\": \"Acme Co\",{Environment.NewLine}  \"Products\": [{Environment.NewLine}    {{{Environment.NewLine}      \"Name\": \"Anvil\",{Environment.NewLine}      \"Price\": 50{Environment.NewLine}    }}{Environment.NewLine}  ]{Environment.NewLine}}}");
@@ -246,7 +249,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("%0:Anvil%%1:Elbow Grease%");
@@ -299,7 +302,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("%0:Anvil%%1:Elbow Grease%");
@@ -328,7 +331,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request)).Throws<ArgumentNullException>();
+            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object)).Throws<ArgumentNullException>();
         }
     }
 }
\ No newline at end of file
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsLinqTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsLinqTests.cs
index f43e8110..4043bc46 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsLinqTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsLinqTests.cs
@@ -1,7 +1,9 @@
-using System;
-using System.Threading.Tasks;
+using Moq;
 using Newtonsoft.Json.Linq;
 using NFluent;
+using System;
+using System.Threading.Tasks;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using WireMock.Util;
@@ -11,11 +13,13 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithHandlebarsLinqTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
+
         [Fact]
         public async Task Response_ProvideResponse_Handlebars_Linq1_String0()
         {
             // Assign
-            var body = new BodyData { };
+            var body = new BodyData();
 
             var request = new RequestMessage(new UrlDetails("http://localhost:1234/pathtest"), "POST", "::1", body);
 
@@ -25,7 +29,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -55,7 +59,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -85,7 +89,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -115,7 +119,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -140,14 +144,14 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request)).Throws<NotSupportedException>();
+            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object)).Throws<NotSupportedException>();
         }
 
         [Fact]
         public void Response_ProvideResponse_Handlebars_Linq1_Throws_ArgumentNullException()
         {
             // Assign
-            var body = new BodyData { };
+            var body = new BodyData();
 
             var request = new RequestMessage(new UrlDetails("http://localhost:1234"), "POST", "::1", body);
 
@@ -156,14 +160,14 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request)).Throws<ArgumentNullException>();
+            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object)).Throws<ArgumentNullException>();
         }
 
         [Fact]
         public void Response_ProvideResponse_Handlebars_Linq1_Throws_ArgumentException()
         {
             // Assign
-            var body = new BodyData { };
+            var body = new BodyData();
 
             var request = new RequestMessage(new UrlDetails("http://localhost:1234"), "POST", "::1", body);
 
@@ -172,7 +176,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request)).Throws<ArgumentException>();
+            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object)).Throws<ArgumentException>();
         }
 
         [Fact]
@@ -196,7 +200,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -224,7 +228,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsRandomTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsRandomTests.cs
index 4d119153..aa78f166 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsRandomTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsRandomTests.cs
@@ -1,8 +1,9 @@
-using System;
-using System.Linq;
+using System.Linq;
 using System.Threading.Tasks;
+using Moq;
 using Newtonsoft.Json.Linq;
 using NFluent;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using Xunit;
@@ -11,6 +12,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithHandlebarsRandomTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
         private const string ClientIp = "::1";
 
         [Fact]
@@ -30,7 +32,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -53,7 +55,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -75,7 +77,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -99,7 +101,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -121,7 +123,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsRegexTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsRegexTests.cs
index 4f98d351..e9365016 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsRegexTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsRegexTests.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Threading.Tasks;
+using Moq;
 using NFluent;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using WireMock.Util;
@@ -10,6 +12,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithHandlebarsRegexTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
         private const string ClientIp = "::1";
 
         [Fact]
@@ -25,7 +28,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("abc");
@@ -44,7 +47,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("");
@@ -63,7 +66,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("d");
@@ -82,7 +85,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("5000-https");
@@ -101,7 +104,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("");
@@ -120,7 +123,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("x");
@@ -139,7 +142,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act and Assert
-            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request)).Throws<NotSupportedException>();
+            Check.ThatAsyncCode(() => response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object)).Throws<NotSupportedException>();
         }
     }
 }
\ No newline at end of file
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsTests.cs
index fad6d28d..57ca8d1d 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsTests.cs
@@ -2,8 +2,10 @@
 using System.Collections.Generic;
 using System.Text;
 using System.Threading.Tasks;
+using Moq;
 using Newtonsoft.Json;
 using NFluent;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using WireMock.Util;
@@ -18,6 +20,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithHandlebarsTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
         private const string ClientIp = "::1";
 
         [Fact]
@@ -38,7 +41,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(JsonConvert.SerializeObject(responseMessage.BodyData.BodyAsJson)).Equals("{\"x\":\"test /foo_object\"}");
@@ -60,7 +63,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("test http://localhost/foo /foo POSt");
@@ -78,7 +81,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("http://localhost/a/b http://localhost/wiremock/a/b /a/b /wiremock/a/b");
@@ -96,7 +99,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("a wiremock");
@@ -118,7 +121,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("test keya=1 idx=1 idx=2 keyb=5");
@@ -138,7 +141,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithHeader("x", "{{request.headers.Content-Type}}").WithBody("test").WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("test");
@@ -160,7 +163,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithHeader("x", "{{request.headers.Content-Type}}", "{{request.url}}").WithBody("test").WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("test");
@@ -185,7 +188,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).Equals("test http://localhost:1234 1234 http localhost");
@@ -209,7 +212,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(JsonConvert.SerializeObject(responseMessage.BodyData.BodyAsJson)).Equals("[\"first\",\"/foo_array\",\"test 1\",\"test 2\",\"last\"]");
@@ -226,7 +229,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithBodyFromFile(@"c:\\{{request.query.MyUniqueNumber}}\test.xml"); // why use a \\ here ?
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsFile).Equals(@"c:\1\test.xml");
@@ -253,7 +256,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithBodyFromFile(@"c:\\{{JsonPath.SelectToken request.body " + jsonPath + "}}\\test.json"); // why use a \\ here ?
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsFile).Equals(@"c:\1\test.json");
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsXegerTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsXegerTests.cs
index abca4648..869f2d75 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsXegerTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsXegerTests.cs
@@ -1,6 +1,8 @@
 using System.Threading.Tasks;
+using Moq;
 using Newtonsoft.Json.Linq;
 using NFluent;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using Xunit;
@@ -9,6 +11,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithHandlebarsXegerTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
         private const string ClientIp = "::1";
 
         [Fact]
@@ -26,7 +29,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
@@ -49,7 +52,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
                 .WithTransformer();
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             JObject j = JObject.FromObject(responseMessage.BodyData.BodyAsJson);
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHeadersTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHeadersTests.cs
index ad596373..448591d8 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHeadersTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHeadersTests.cs
@@ -1,6 +1,8 @@
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using Moq;
 using NFluent;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.ResponseBuilders;
 using WireMock.Util;
@@ -10,6 +12,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithHeadersTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
         private const string ClientIp = "::1";
 
         [Theory]
@@ -23,7 +26,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             IResponseBuilder builder = Response.Create().WithHeader(headerName, headerValue);
 
             // Act
-            var response = await builder.ProvideResponseAsync(requestMock);
+            var response = await builder.ProvideResponseAsync(requestMock, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(response.Headers[headerName].ToString()).Equals(headerValue);
@@ -39,7 +42,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             IResponseBuilder builder = Response.Create().WithHeader(headerName, headerValues);
 
             // Act
-            var response = await builder.ProvideResponseAsync(requestMock);
+            var response = await builder.ProvideResponseAsync(requestMock, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(response.Headers[headerName].ToArray()).Equals(headerValues);
@@ -54,7 +57,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithHeaders(headers);
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.Headers["h"]).ContainsExactly("x");
@@ -69,7 +72,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithHeaders(headers);
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.Headers["h"]).ContainsExactly("x");
@@ -84,7 +87,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithHeaders(headers);
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.Headers["h"]).ContainsExactly("x");
diff --git a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithProxyTests.cs b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithProxyTests.cs
index 28b3aafb..a920f27c 100644
--- a/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithProxyTests.cs
+++ b/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithProxyTests.cs
@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using Moq;
 using NFluent;
+using WireMock.Handlers;
 using WireMock.Models;
 using WireMock.RequestBuilders;
 using WireMock.ResponseBuilders;
@@ -13,6 +15,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
 {
     public class ResponseWithProxyTests : IDisposable
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
         private readonly FluentMockServer _server;
         private readonly Guid _guid;
 
@@ -34,7 +37,7 @@ namespace WireMock.Net.Tests.ResponseBuilders
             var response = Response.Create().WithProxy(_server.Urls[0]);
 
             // Act
-            var responseMessage = await response.ProvideResponseAsync(request);
+            var responseMessage = await response.ProvideResponseAsync(request, _fileSystemHandlerMock.Object);
 
             // Assert
             Check.That(responseMessage.BodyData.BodyAsString).IsEqualTo("{\"p\":42}");
diff --git a/test/WireMock.Net.Tests/Serialization/MappingConverterTests.cs b/test/WireMock.Net.Tests/Serialization/MappingConverterTests.cs
index 1a351e5b..ebe68c33 100644
--- a/test/WireMock.Net.Tests/Serialization/MappingConverterTests.cs
+++ b/test/WireMock.Net.Tests/Serialization/MappingConverterTests.cs
@@ -1,5 +1,7 @@
-using System;
-using NFluent;
+using FluentAssertions;
+using Moq;
+using System;
+using WireMock.Handlers;
 using WireMock.RequestBuilders;
 using WireMock.ResponseBuilders;
 using WireMock.Serialization;
@@ -9,19 +11,41 @@ namespace WireMock.Net.Tests.Serialization
 {
     public class MappingConverterTests
     {
+        private readonly Mock<IFileSystemHandler> _fileSystemHandlerMock = new Mock<IFileSystemHandler>();
+
         [Fact]
-        public void MappingConverter_ToMappingModel()
+        public void ToMappingModel()
         {
             // Assign
             var request = Request.Create();
             var response = Response.Create();
-            var mapping = new Mapping(Guid.NewGuid(), "", null, request, response, 0, null, null, null);
+            var mapping = new Mapping(Guid.NewGuid(), "", null, _fileSystemHandlerMock.Object, request, response, 0, null, null, null);
 
             // Act
             var model = MappingConverter.ToMappingModel(mapping);
 
             // Assert
-            Check.That(model).IsNotNull();
+            model.Should().NotBeNull();
+            model.Priority.Should().BeNull();
+            model.Response.BodyAsJsonIndented.Should().BeNull();
+            model.Response.UseTransformer.Should().BeNull();
+        }
+
+        [Fact]
+        public void ToMappingModel_WithPriority_ReturnsPriority()
+        {
+            // Assign
+            var request = Request.Create();
+            var response = Response.Create().WithBodyAsJson(new { x = "x" }).WithTransformer();
+            var mapping = new Mapping(Guid.NewGuid(), "", null, _fileSystemHandlerMock.Object, request, response, 42, null, null, null);
+
+            // Act
+            var model = MappingConverter.ToMappingModel(mapping);
+
+            // Assert
+            model.Should().NotBeNull();
+            model.Priority.Should().Be(42);
+            model.Response.UseTransformer.Should().BeTrue();
         }
     }
 }
\ No newline at end of file