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Rony.Net

Rony.Net is a mock server for testing .NET code that talks over the network. Start a real TCP, TCP + SSL/TLS, UDP or Unix socket server inside your test, tell it how to answer, point your client at it, and then check what your client sent.

using var server = new MockServer(new TcpServer(0));   // 0 = any free port
server.Mock.Send("PING").Receive("PONG");
server.Start();

// ... run the code under test against 127.0.0.1:server.Port ...

server.Should().HaveReceived("PING", Times.Once());

Why use it

• Real sockets. Your client code runs unchanged: no interfaces to extract, no fake streams.
• Any protocol. Text or binary, one request per connection or many, delimited or length-prefixed messages.
• Realistic servers. Greetings, pushed messages, and stateful scenarios such as "log in before listing".
• Failure testing. Slow responses, dropped connections, silence, and responses that change over time.
• Assertions on the client. Check which requests were sent, how often and in which order, how it used its connections, or wait until a request arrives. Fluent assertions included.
• Easy debugging. A log of everything the server saw and did, written to your test output.
• Test-friendly. Free ports for parallel tests, thread-safe configuration, clear failure messages.

Install

dotnet add package Rony.Net

Works with .NET Core 3.x, .NET 5 and every later version (the package targets netstandard2.1 and net8.0). It works with any test framework: xUnit, NUnit, MSTest or none at all. Optional packages (Rony.Net.Xunit, Rony.Net.Xunit.v3, Rony.Net.NUnit, Rony.Net.MSTest) remove the setup code; see Test Framework Integration. To run a mock server without writing code, install the rony tool (Rony.Net.Cli) or use its Docker image ghcr.io/archofthings/rony: see Standalone Server. To start the tool in a Docker container from a test, use Rony.Net.Testcontainers: see Testcontainers.

Documentation

Start here
Getting Started	Install, first test, the namespaces you need
Servers	TCP, UDP and Unix socket servers, IPv6, addresses and properties
SSL and TLS	Secure servers, certificates for tests
Ports and Lifecycle	Free ports, start/stop/restart, parallel tests
Connections and Framing	Persistent connections, delimiters, length prefixes, custom framing
Connections and Push	Greetings, pushed messages, inspecting and checking connections

Configure responses
Configuring Responses	Text, bytes, computed responses, a default response
Request Matching	Exact, regex and predicate matching, and precedence
Response Sequences	A different response each time
Simulating Failures	Delays, disconnects, silence, flaky servers
Stateful Scenarios	Rules that depend on what happened before (InState, GoTo)
Record and Replay	Record a real server with RecordingProxy, replay it with server.Replay(...)
Configuration Files	Describe the server and its rules in a JSON file, load it with MockServer.FromFile(...)
Standalone Server	The rony command-line tool and its Docker image (ghcr.io/archofthings/rony): run, record and replay without code, with a journal and a control endpoint to check what the mock received. Scenarios for development, teams without .NET, CI and Docker Compose; the Rony.Net.Testcontainers module

Check your client
Verifying Requests	server.Should() assertions, Times, order, strict mode, inspecting requests
Waiting for Requests	WaitForRequestAsync instead of Thread.Sleep
Logging and Diagnostics	See what the server received and did, and why
Test Framework Integration	Base classes for xUnit, NUnit and MSTest

More
Recipes	Testing a real client class, retries, timeouts, sharing a server between tests
Custom Listeners	Plug in your own transport
API Reference	Every public type and member
Troubleshooting	Common problems and answers
Known Issues	What the library and the rony tool do not do, or do in a surprising way
Upgrading to 1.0	Changes from 0.x

Runnable examples

Every example in this wiki is a passing test in the samples project. Clone the repository and run dotnet test samples/Rony.Samples to try them.