Integration testing with in-memory IdentityServer

Question

I have an API that uses IdentityServer4 for token validation. I want to unit test this API with an in-memory TestServer. I\'d like to host the IdentityServer in the in-memor

Answer 1

None of the other answers worked for me because they rely on 1) a static field to hold your HttpHandler and 2) the Startup class to have knowledge that it may be given a test handler. I've found the following to work, which I think is a lot cleaner.

First create an object that you can instantiate before your TestHost is created. This is because you won't have the HttpHandler until after the TestHost is created, so you need to use a wrapper.

public class TestHttpMessageHandler : DelegatingHandler
{
    private ILogger _logger;

    public TestHttpMessageHandler(ILogger logger)
    {
        _logger = logger;
    }

    protected override async Task SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        _logger.Information($"Sending HTTP message using TestHttpMessageHandler. Uri: '{request.RequestUri.ToString()}'");

        if (WrappedMessageHandler == null) throw new Exception("You must set WrappedMessageHandler before TestHttpMessageHandler can be used.");
        var method = typeof(HttpMessageHandler).GetMethod("SendAsync", BindingFlags.Instance | BindingFlags.NonPublic);
        var result = method.Invoke(this.WrappedMessageHandler, new object[] { request, cancellationToken });
        return await (Task)result;
    }

    public HttpMessageHandler WrappedMessageHandler { get; set; }
}

Then

var testMessageHandler = new TestHttpMessageHandler(logger);

var webHostBuilder = new WebHostBuilder()
...
                        services.PostConfigureAll(options =>
                        {
                            options.Audience = "http://localhost";
                            options.Authority = "http://localhost";
                            options.BackchannelHttpHandler = testMessageHandler;
                        });
...

var server = new TestServer(webHostBuilder);
var innerHttpMessageHandler = server.CreateHandler();
testMessageHandler.WrappedMessageHandler = innerHttpMessageHandler;