How to mock a web api for testing

Question

I have a class library which is included some DelegationHandlers, It is simple, get the request, add some headers based on request content and pass the request down.

So what I needed is write unit tests for my library. I'm using .NET Core 2.1 and xunit, I was wondering if there is a way to mock a web server, then I can send a request to this web server using my library and check the result of my request? Any Idea how could I mock a web server (app)? or how could I test my library by sending a http request?

Answer 1

I found a solution here, I share it maybe useful for others.

public void GivenThereIsAServiceRunningOn(string baseUrl, string basePath, RequestDelegate del)
{
    _builder = new WebHostBuilder()
        .UseUrls(baseUrl)
        .UseKestrel()
        .UseContentRoot(Directory.GetCurrentDirectory())
        .UseIISIntegration()
        .Configure(app =>
        {
            app.UsePathBase(basePath);
            app.Run(del);
        })
        .Build();

    _builder.Start();
}

The same WebHostBuilder we used in Integration Tests, now we could pass RequestDelegate to run the app:

GivenThereIsAServiceRunningOn(baseUrl, basePath, async context =>
{
    _downstreamPath = !string.IsNullOrEmpty(context.Request.PathBase.Value) ? context.Request.PathBase.Value : context.Request.Path.Value;

    if (_downstreamPath != basePath)
    {
        context.Response.StatusCode = statusCode;
        await context.Response.WriteAsync("downstream path didn't match base path");
    }
    else
    {
        context.Response.StatusCode = statusCode;
        await context.Response.WriteAsync(responseBody);
    }
});