Response Sequences

Use Then(...) to return a different response each time the same request arrives. When the sequence runs out, the last response repeats.

using var server = new MockServer(new TcpServer(0));
server.Mock.Send("status").Receive("starting").Then("starting").Then("ready");
server.Start();

using var client = await TcpTestClient.ConnectAsync(server.Port);
Assert.Equal("starting", await client.SendAndReceiveAsync("status"));
Assert.Equal("starting", await client.SendAndReceiveAsync("status"));
Assert.Equal("ready", await client.SendAndReceiveAsync("status"));
Assert.Equal("ready", await client.SendAndReceiveAsync("status"));   // the last one repeats

This is useful for testing:

• Polling: "busy, busy, ready".
• Retries: "fail, fail, succeed"; see Simulating Failures.
• Paging: "page 1, page 2, end".
• State changes: "logged out" after a logout command.

What a step can be

Every step in a sequence can be any kind of response:

server.Mock.Send("data")
    .Receive("text")                          // text
    .Then(new byte[] { 0x01 })                // bytes
    .Then(text => text.ToUpper())             // computed from the request
    .Then(bytes => bytes.Reverse().ToArray())
    .ThenNoReply()                            // silence
    .ThenDisconnect();                        // close the connection

After(delay) and AndDisconnect() apply to the step just before them:

server.Mock.Send("data")
    .Receive("late").After(TimeSpan.FromMilliseconds(300))
    .Then("quick");

A sequence can also start with Disconnect() or NoReply():

server.Mock.Send("pay").Disconnect().ThenDisconnect().Then("PAID");

Sequences or functions?

A function in Receive(...) runs on every request, so it can count calls by itself:

var counter = 0;
server.Mock.Send("next").Receive(_ => $"#{++counter}");

Use Then(...) for a short fixed script, and a function for an open-ended pattern.

Notes

• A sequence belongs to its configuration, not to a connection: every client moves through the same sequence.
• Config.CallCount tells you how many steps have been used.
• server.Mock.Reset() removes the configuration, sequence included.

Runnable code: SequenceAndFailureSamples.cs