I am trying to mock out a user in my asp.net core web api application (right now I do not have any information how the user will authenticate, but I need to test te migrated API). For that I created a sample application to try it.

using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.Cookies;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

builder.Services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
builder.Services.AddHttpContextAccessor();

builder.Services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
                .AddCookie(options =>
                {
                    options.ExpireTimeSpan = TimeSpan.FromMinutes(20);
                    options.SlidingExpiration = true;
                    options.AccessDeniedPath = "/Forbidden/";
                });


var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthentication();
app.UseAuthorization(); ;

app.MapControllers();

using var scope = app.Services.CreateScope();
var httpContextAccessor = scope.ServiceProvider.GetRequiredService<IHttpContextAccessor>();

if (httpContextAccessor is not null)
{
    httpContextAccessor.HttpContext ??= new DefaultHttpContext();
    var identity = new ClaimsIdentity(CookieAuthenticationDefaults.AuthenticationScheme, ClaimTypes.Email, ClaimTypes.Role);
    identity.AddClaims(new List<Claim>
    {
        new(JwtRegisteredClaimNames.Sub, "JhonDoe"),
        new(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
        new(JwtRegisteredClaimNames.Email, "[email protected]")
    });

    var principal = new ClaimsPrincipal(identity);

    var authProperties = new AuthenticationProperties
    {
        IsPersistent = true,  
    };

    await httpContextAccessor!.HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, principal, authProperties);
}

app.Run();

When the line: httpContextAccessor!.HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, principal, authProperties); executes, I got the following error message:

Unhandled exception. System.ArgumentNullException: Value cannot be null. (Parameter ‘provider’)
at System.ThrowHelper.Throw(String paramName)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetService[T](IServiceProvider provider)
at Microsoft.AspNetCore.Authentication.AuthenticationHttpContextExtensions.GetAuthenticationService(HttpContext context)
at Microsoft.AspNetCore.Authentication.AuthenticationHttpContextExtensions.SignInAsync(HttpContext context, String scheme, ClaimsPrincipal principal, AuthenticationProperties properties)
at Program.$(String[] args) in D:DesktopHttpContextTestAppProgram.cs:line 83
at Program.(String[] args)

Any idea?