TitanShark.Thresher

Provides extendable Interception Mechanism for HttpClient.

TitanShark.Thresher.Core

Introduces Fundamentals for intercepting HttpClient via customization of HttpClientHandler.

Nuget Package: https://www.nuget.org/packages/TitanShark.Thresher.Core/

Minimum DotNet's Version required:

.Net Framework 4.6.2
.Net Standard 2.0
.Net 5.0 (yayy! IoI)

Core concepts:

InterceptableHttpClientHandler is your new friend :-), as it provides you the possibilities for customizing behaviors of HttpClientHandler via your own Interceptors (IInterceptor).

Interceptors will be executed by an InterceptorRunner. For your choice, SequentialInterceptorsRunner and ParallelInterceptorsRunner were built-in.

Use case 1: Mocking Request (in Unit-Test)

If you need to mock the Response in your Unit-Test, you should write your own Transmitter, like in the below example:

const string responseContentText = "Hello World!";
var transmitter = new Transmitter
    (
        (callId, request, cancellationToken) =>
        {
            _output.WriteLine($"Request to '{request.RequestUri}' was sent out.");

            return Task.FromResult(new HttpResponseMessage(System.Net.HttpStatusCode.Created) 
            { 
                Content = new StringContent(responseContentText) 
            });
        }
    );
var handler = new InterceptableHttpClientHandler(transmitter: transmitter);
var sut = new HttpClient(handler);

More details

Use case 2: Recording and replaying your Request/Reponse

For tracing, backup or anylazing, you might need to capture all Requests sent out and corresponding Responses received. Then Recorder and Replayer are your weapons.

Generally, Recorder is just a special Interceptor which saves passed-thru Request and Response as Record into the target Persistence. In the other direction, Replayer filters Record in Persistence to form a Snapshot for replaying.

// recording
var persistence = new InMemoryRecordsPersistence();
var recorder = new Recorder(persistence);
var handler = new InterceptableHttpClientHandler(
    transmitter: transmitter, 
    interceptorsRunner: new SequentialInterceptorsRunner(recorder));
var client = new HttpClient(handler);

// code for sending Requests
//...

// replaying Requests with given Response's Status Codes
var snapshot = await persistence.Snapshot(
                CancellationToken.None, 
                started, ended, 
                new[] { HttpStatusCode.BadRequest, HttpStatusCode.NotFound });
var replayer = new Replayer(new SequentialReplayingStrategy(), client, snapshot);
replayer.Start();

More details

You are not limited to InMemoryRecordsPersistence; just write a new Persistence for your own need. All you have to do is adding a new implementation of IRecordsPersistence.

By default, SystemJsonRecordSerializer (powered by System.Text.Json - a built-in, lightweight JSON-Lib of .Net Framework) is employed for serializing/deserializing Record. You can however plug your own Serialization Mechanism (implementing IRecordSerializer) into your Persistence's Instance. An example for using Newtonsoft.Json is given here.