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Tutorial on how to write integration test for SignalR hub. Client is Blazor

IntegrationTestForSignalR

Tutorial on how to write integration test for SignalR hub. Client is Blazor

Instructions

1. Complete this tutorial - https://learn.microsoft.com/en-us/aspnet/core/blazor/tutorials/signalr-blazor?view=aspnetcore-7.0&tabs=visual-studio&pivots=webassembly

Before going to next step I recommend you place literals related to signalr to constants in my case
I created SignalRConstants class with two constants. First one is SendMessageHandlerName and second one is
ChatHubRouteName

2. Add test project. In my case I added xUnit test project
3. Add link to your server project. In my case I add link to the BlazorSignalR.Server
4. Add this list of NuGet packages:

• Moq
• FluentAssertion
• Microsoft.AspNetCore.Mvc.Testing
• Microsoft.AspNetCore.SignalR.Client

5. Add test class with name - ChatHubTest

IMPORTANT NOTE: All next code changes will take place in one class, in ChatHubTest class

6. Derive class from IClassFixture<WebApplicationFactory<Program>> so your class will look like this:

public class ChatHubTests : IClassFixture<WebApplicationFactory<Program>>
{}

Program class is the entry point of my BlazorSignalR.Server project

By implementing IClassFixture<T> interface you create one context of T for whole tests in the current class
more you can read here - https://xunit.net/docs/shared-context#class-fixture

WebApplicationFactory<TProgram> is the class that create the system that will be under the test, where
TProgram is the class that contains the startup logic of your application. There is a big reason why you should you use it, please read this article about why you should consider to use this class if you do integration test on .NET 7

7. Add constructor to your class. Constructor should accept WebApplicationFactory<Program> factory so your code will be like this:

public class ChatHubTests : IClassFixture<WebApplicationFactory<Program>>
{
    private readonly WebApplicationFactory<Program> _factory;

    public ChatHubTests(WebApplicationFactory<Program> factory)
    {
        _factory = factory;
    }
}

8. Add StartConnectionAsync method that create connection with SignlaR hub - ChatHub. Result:

private async Task<HubConnection> StartConnectionAsync(HttpMessageHandler handler, string hubName)
{
    var hubConnection = new HubConnectionBuilder()
        .WithUrl($"ws://localhost/{hubName}", o =>
        {
            o.HttpMessageHandlerFactory = _ => handler;
        })
        .Build();

    await hubConnection.StartAsync();

    return hubConnection;
}

You can see that url contains "ws" instead of "https". This is important since signlar prefered way of communication is web socket

9. Add the test:

[Fact]
public async Task ShouldNotifySubscribers()
{
    _factory.CreateClient(); // You need to call this procedure in order to create server
    var mockHandler = new Mock<Action<string, string>>(); 

    // Arrange

    var connection = await StartConnectionAsync(_factory.Server.CreateHandler(), SignalRConstants.ChatHubRouteName);
    //Register handler with some name, message will be sent from server to the handler with this name
    connection.On(SignalRConstants.SendMessageHandlerName, mockHandler.Object);

    var sourceUserName = "super_user";
    var sourceMessage = "Hello World!!";

    // Act
    // Send message to the ChatHub(to the server), to the SendMessage method(method with such name exist in ChatHub)
    await connection.InvokeAsync(nameof(ChatHub.SendMessage), sourceUserName, sourceMessage);

    // Assert
    // Make sure that handler was called once and that handler have recieved correct input values
    mockHandler.Verify(x => x(It.Is<string>(userName => userName == sourceUserName), It.Is<string>(message => message == sourceMessage)), Times.Once);
}