Set environment in integration tests

I want to set environment in my integration tests using WebApplicationFactory. by defualt, env is set to Development. Code of my web application factory looks like this:

    public class CustomWebApplicationFactory<TStartup> : WebApplicationFactory<TStartup>
        where TStartup : class
    {
        protected override void ConfigureWebHost(IWebHostBuilder builder)
        {
            builder.UseSolutionRelativeContentRoot(AppContext.BaseDirectory);

            base.ConfigureWebHost(builder);
        }

        protected override IWebHostBuilder CreateWebHostBuilder()
        {
            return WebHost.CreateDefaultBuilder()
                .UseStartup<TStartup>()
                .UseEnvironment("test"); // i want to launch `test` environment while im
                                         // testing my app
        }
    }

When i start to debug Startup class (while i run tests) i still getting Development environment:

        public Startup(IHostEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", false, true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", true)
                // env.EnvironmentName is set to 'Development' while i set it to 'test'
                // in my WebApplicationFactory
                .AddEnvironmentVariables();

            Configuration = builder.Build();
        }

How to set environment in WebApplicationFactory properly?