Waiting for Requests

Waiting for Requests

When your code sends in the background (a heartbeat, a log shipper, a fire-and-forget message), a test needs to wait for the request to arrive. Don't use Thread.Sleep or Task.Delay: they make tests slow, and still flaky. Wait for the request itself instead:

using var server = new MockServer(new UdpServer("127.0.0.1", 0));
server.Mock.Send("").NoReply();
server.Start();

StartHeartbeat(server.Port);   // your code, sending in the background

var request = await server.Mock.WaitForRequestAsync("HEARTBEAT", TimeSpan.FromSeconds(5));

Assert.Equal("HEARTBEAT", request.BodyString);

The methods

await server.Mock.WaitForRequestAsync();                               // any request
await server.Mock.WaitForRequestAsync("HEARTBEAT");                    // exact text
await server.Mock.WaitForRequestAsync(new byte[] { 0x01 });            // exact bytes
await server.Mock.WaitForRequestAsync(r => r.Body.Length > 100);       // a predicate
var requests = await server.Mock.WaitForRequestsAsync(count: 3);       // at least 3 requests in total

• They return the matching ReceivedRequest, or the list of requests for WaitForRequestsAsync.
• They include requests that arrived before you started waiting, so there is no race between sending and waiting.
• The timeout defaults to 5 seconds. Pass your own as the second argument.
• All of them accept a CancellationToken as the last argument.

To wait for connections instead, see Connections and Push: server.WaitForConnectionAsync(), server.WaitForConnectionsAsync(count) and connection.WaitForCloseAsync().

With FailOnUnmatched, a wait stops with a MockVerificationException as soon as an unexpected request arrives.

Timeouts

When the timeout expires, a TimeoutException explains what was expected and lists what did arrive:

var error = await Assert.ThrowsAsync<TimeoutException>(
    () => server.Mock.WaitForRequestAsync("expected", TimeSpan.FromMilliseconds(200)));

Expected request "expected" within 00:00:00.2000000, but it was not received.
Received requests:
  1. "something else" (unmatched)

Waiting, then verifying

Wait for the last request you expect, then verify the rest:

await server.Mock.WaitForRequestAsync("COMMIT");
server.Should().HaveReceived("BEGIN", Times.Once());
server.Should().HaveReceived(r => r.BodyString.StartsWith("INSERT"), Times.Exactly(3));

Runnable code: VerificationSamples.cs