public void BuildAndDispose() { var vals = new Dictionary <string, string> { { "ENV", "Dev" }, }; var builder = new ConfigurationBuilder() .AddInMemoryCollection(vals); var config = builder.Build(); var expected = "MY_TEST_ENVIRONMENT"; var host = new WebHostBuilder() .UseConfiguration(config) .UseEnvironment(expected) .UseServer(new TestServer()) .UseStartup("Microsoft.AspNetCore.Hosting.Tests") .Build(); host.Dispose(); }