Dependancy Injection not working with ASPNETCore.TestHost

Question

I have been struggling many hours with this issue. My WebAPI App works fine on local machine and production server but fails during an integration test of a controller that has dependency injection. Everything looks very clean and I have no idea why this is not working.

So here come the modules: The controller:

public SurveyController(IBoatInspectorRepository<Survey> repository)
{
    _repository = repository;
}

[HttpGet]
public IEnumerable<string> Get()
{
    return new string[] {"value1", "value2"};
}

The start up:

public void ConfigureServices(IServiceCollection services)
{
    services.AddScoped<IBoatInspectorRepository<Survey>, BoatInspectorRepository<Survey>>();
}

The test:

[Test]
public async Task GetSurveyDb_NullReturn_ReturnNotFound()
{  
    using (var testServer = CreateTestServer())
    {
        var client = testServer.CreateClient();
        var value = await client.GetAsync("/api/survey/");
    }
}  

private TestServer CreateTestServer()
{
    var builder = new WebHostBuilder()                
        .UseStartup<Startup>()
        .ConfigureServices(services => 
            services.AddScoped<IBoatInspectorRepository<Survey>, BoatInspectorRepository<Survey>>());

    return new TestServer(builder);                
}

If I debug this the debugger doesn't even go into the controller constructor. If I comment out the constructor and create an empty one everything works fine so it is 100% something to do with the dependency injection. Please help. Thank you.

---

UPDATE 1

So it seems that it is a problem with context initialization because if I do the following the constructor isn't initialized either.

    public SurveyController(BoatInspectorContext context)
    {
     //debuger doesn't go inside here so must be something with context   
    }

Answer 1

So after two sleepless nights I found the fault... For some unovious reason the test server was not able to read the connection string to my db from apsettings.json using

.AddDbContext<BoatInspectorContext>(
                opt=>opt.UseNpgsql(Configuration.GetConnectionString("BoatInspectorConnectionString")));

so all I had to to was

.AddDbContext<BoatInspectorContext>(
                opt => opt.UseNpgsql(
                    connectionString:
                    "my_magic_connection_string"));

For some reason this error wasn't coming up anywhere or maybe I didn't see it so after I spoted what it said it was pretty obvious.