Unit testing that the swagger doc is correct without starting a server - swashbuckle.aspnetcore

Question

I'd like to test that the swagger document is correct for my application (mainly, because I've added a strategy to generate custom OperationIds and I want to ensure they are correctly unique)
However, the only solutions I found are all using a "real" server (cf https://stackoverflow.com/a/52521454/1545567), which is not an option for me since I do not have the database, message bus, etc... when I launch the unit tests in CI...
At the moment, I have the following but it always generate 0 paths and 0 models ...
using FluentAssertions;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.OpenApi.Models;
using SampleCheckIn;
using Swashbuckle.AspNetCore.SwaggerGen;
using System;
using System.Linq;
using Xunit;
using SampleCheckIn.Def;
using Service.Utils;
using Swashbuckle.AspNetCore.Swagger;
using Microsoft.Extensions.Logging;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.FileProviders;
namespace D4Interop.Tests
{
public class TmpTest
{
[Fact]
public void Tmp()
{
var controllers = typeof(Startup).Assembly.GetTypes().Where(x => IsController(x)).ToList();
controllers.Any().Should().BeTrue();
var services = new ServiceCollection();
controllers.ForEach(c => services.AddScoped(c));
services.AddLogging(logging => logging.AddConsole());
services.AddControllers(); //here, I've also tried AddMvcCore and other ASP methods...
services.AddSwaggerGen(c =>
{
c.SwaggerDoc("api", new OpenApiInfo { Title = Constants.SERVICE_NAME, Version = "_", Description = Constants.SERVICE_DESC });
//c.OperationFilter<SwaggerUniqueOperationId>(); //this is my filter that ensures the operationId is unique
c.CustomOperationIds(apiDesc =>
{
return apiDesc.TryGetMethodInfo(out var methodInfo) ? methodInfo.Name : null;
});
});
services.AddSingleton<IWebHostEnvironment>(new FakeWebHostEnvironment());
var serviceProvider = services.BuildServiceProvider();
var swaggerProvider = serviceProvider.GetRequiredService<ISwaggerProvider>();
var swagger = swaggerProvider.GetSwagger("api");
swagger.Should().NotBeNull();
swagger.Paths.Any().Should().BeTrue();
}
private bool IsController(Type x)
{
return typeof(Microsoft.AspNetCore.Mvc.ControllerBase).IsAssignableFrom(x);
}
}
internal class FakeWebHostEnvironment : IWebHostEnvironment
{
public FakeWebHostEnvironment()
{
}
public IFileProvider WebRootFileProvider { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
public string WebRootPath { get => "/root"; set => throw new NotImplementedException(); }
public string EnvironmentName { get => "dev"; set => throw new NotImplementedException(); }
public string ApplicationName { get => "app"; set => throw new NotImplementedException(); }
public string ContentRootPath { get => "/"; set => throw new NotImplementedException(); }
public IFileProvider ContentRootFileProvider { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
}
}

Answer 1

Ok, I've finally found that I just need to mix the linked answer with my code :
[Fact]
public async Task TestSwagger()
{
var server = Host.CreateDefaultBuilder()
.ConfigureWebHostDefaults(options => { options.UseStartup<Startup>(); })
.Build();
var swagger = server.Services
.GetRequiredService<ISwaggerProvider>()
.GetSwagger("xxx"); //xxx should be the name of your API
swagger.Should().NotBeNull();
swagger.Paths.Any().Should().BeTrue();
swagger.Components.Schemas.Should().NotBeNull();
}