Testing SignalR Applications with Integration Tests

In the last days, I have been dealing with a chat prototype that uses SignalR. I’ve been trying to follow the test-driven development (TDD) approach as I like this design pattern. I always try to find a way to test my code and define use cases so that when I’m refactoring or writing code, as long as the tests pass, I know everything is fine.

When doing ORM-related problems, testing is relatively easy because you can set up a memory provider, have a clean database, perform your operations, and then revert to normal. But when testing APIs, there are several approaches.

Some approaches are more like unit tests where you get a controller and directly pass values by mocking them. However, I prefer tests that are more like integration tests – for example, I want to test a scenario where I send a message to a chat and verify that the message send event was real. I want to show the complete set of moving parts and make sure they work together.

In this article, I want to explore how to do this type of test with REST APIs by creating a test host server. This test host creates two important things: a handler and an HTTP client. If you use the HTTP client, each HTTP operation (POST, GET, etc.) will be sent to the controllers that are set up for the test host. For the test host, you do the same configuration as you would for any other host – you can use a startup class or add the services you need and configure them.

I wanted to do the same for SignalR chat applications. In this case, you don’t need the HTTP client; you need the handler. This means that each request you make using that handler will be directed to the hub hosted on the HTTP test host.

Here’s the code that shows how to create the test host:

// ARRANGE
// Build a test server
var hostBuilder = new HostBuilder()
    .ConfigureWebHost(webHost =>
    {
        webHost.UseTestServer();
        webHost.UseStartup<Startup>();
    });

var host = await hostBuilder.StartAsync();

//Create a test server
var server = host.GetTestServer();

And now the code for handling SignalR connections:

         // Create SignalR connection
         var connection = new HubConnectionBuilder()
             .WithUrl("http://localhost/chathub", options =>
             {
                 // Set up the connection to use the test server
                 options.HttpMessageHandlerFactory = _ => server.CreateHandler();
             })
             .Build();

         string receivedUser = null;
         string receivedMessage = null;

         // Set up a handler for received messages
         connection.On<string, string>("ReceiveMessage", (user, message) =>
         {
             receivedUser = user;
             receivedMessage = message;
         });

//if we take a closer look, we can see the creation of the test handler "server.CreateHandler"
var connection = new HubConnectionBuilder() .WithUrl("http://localhost/chathub", options => 
{ 
// Set up the connection to use the test server 
options.HttpMessageHandlerFactory = _ => server.CreateHandler(); 
}) .Build();

 

Now let’s open a SignalR connection and see if we can connect to our test server:

          string receivedUser = null;
          string receivedMessage = null;

          // Set up a handler for received messages
          connection.On<string, string>("ReceiveMessage", (user, message) =>
          {
              receivedUser = user;
              receivedMessage = message;
          });

          // ACT
          // Start the connection
          await connection.StartAsync();

          // Send a test message through the hub
          await connection.InvokeAsync("SendMessage", "TestUser", "Hello SignalR");

          // Wait a moment for the message to be processed
          await Task.Delay(100);

          // ASSERT
          // Verify the message was received correctly
          Assert.That("TestUser"==receivedUser);
          Assert.That("Hello SignalR"== receivedMessage);

          // Clean up
          await connection.DisposeAsync();

 

You can find the complete source of this example here: https://github.com/egarim/TestingSignalR/blob/master/UnitTest1.cs