aspnetcore/test/Microsoft.AspNetCore.Mvc.FunctionalTests/DataAnnotationTests.cs

using System.Net;
using System.Threading.Tasks;
using RazorWebSite;
using Microsoft.AspNetCore.Hosting;
using Xunit;
using System.Linq;
using System.Net.Http;

namespace Microsoft.AspNetCore.Mvc.FunctionalTests
{
    public class DataAnnotationTests : IClassFixture<MvcTestFixture<StartupDataAnnotations>>
    {
        private HttpClient Client { get; set; }

        public DataAnnotationTests(MvcTestFixture<StartupDataAnnotations> fixture)
        {
            var factory = fixture.Factories.FirstOrDefault() ?? fixture.WithWebHostBuilder(builder =>
            {
                builder.UseStartup<StartupDataAnnotations>();
            });
            Client = factory.CreateDefaultClient();
        }

        private const string EnumUrl = "http://localhost/Enum/Enum";

        [Fact]
        public async Task DataAnnotationLocalizationOfEnums_FromDataAnnotationLocalizerProvider()
        {
            // Arrange & Act
            var response = await Client.GetAsync(EnumUrl);
            var content = await response.Content.ReadAsStringAsync();

            // Assert
            Assert.Equal(HttpStatusCode.OK, response.StatusCode);
            Assert.Contains("FirstOptionDisplay from singletype", content);
        }
    }
}