Unit testing an external HTTP request in .NET

Question

I have the following method:

  private async Task<Result> TryGetResult (string request)
        {
            var httpClient = new HttpClient(); 
            var result = await httpClient.GetAsync(request);
            if (result.IsSuccess)
            {
                var body = await result.Content.ReadAsStringAsync();
                var deserializedResult = JsonConvert.DeserializeObject<Result>(body);
                return deserializedResult ;
            }

            if ( result.StatusCode == (HttpStatusCode)429 )
            {
                await Task.Delay(TimeSpan.FromSeconds(1));
                return await TryGetResult(request);
            }
        }

This takes in this string request: var request = $"https://atlas.microsoft.com/search/address/json ... //(private keys omitted)

I want to unit test the method and stub out the request so that I don't make a real call. I have limited experience unit testing C# and am struggling to work out how to stub this? Please can anyone point me in the right direction?

I have tried looking at similar articles and googling but cannot find the stubbing of a string request like this and wonder if I'm going in the wrong direction with trying to test?

Daniel A. White · Accepted Answer · 2020-07-13 16:40:13Z

1

You should allow for injection of a HttpClient from the constructor of the class containing TryGetResult

public class YourClass // might want to implement IDisposable?
{
    private readonly HttpClient _client;

    public YourClass()
       : this(new HttpClient());
    {
    }

    public YourClass(HttpClient client)
    {
        _client = client ?? throw new ArgumentNullException(nameof(client));
    }
}

From there, I would suggest mocking the HttpClient with RichardSzalay.MockHttp. That way you can control the full response.

answered Jul 13, 2020 at 16:40

Daniel A. White

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