CODEWITHSUNDEEP
c#polly
Anders Sewerin Johansen
Anders Sewerin Johansen

Reputation: 1666

Adding Polly retry policy to a mocked HttpClient?

So I have to use a library that takes a HttpClient, and may throw a throttling exception in case of a 429 response from the remote system.

I'd like to test a Polly policy that would back off for the requested amount of seconds, but I can't figure out how to modify the test to add a Polly policy.

I looked at this SO question, but my circumstances are different: Testing Polly retry policy with moq

Here's the test that verifies the exception is thrown. I would like to make a different version with a Polly retry policy that won't throw.

using Moq;
using Moq.Protected;
using Polly;
using System.Net;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;

[TestClass]
public class SIGSClientTests
{

    [TestMethod]
    public async Task SigsThrowsOn429()
    {
        var resp = new HttpResponseMessage
        {
            StatusCode = (HttpStatusCode)429,
            Content = new StringContent("{}"),
        };

        resp.Headers.Add("Retry-After", "42");

        var mockMessageHandler = new Mock<HttpMessageHandler>();
        mockMessageHandler.Protected()
            .Setup<Task<HttpResponseMessage>>("SendAsync", ItExpr.IsAny<HttpRequestMessage>(), ItExpr.IsAny<CancellationToken>())
            .ReturnsAsync(resp);

        var client = new HttpClient(mockMessageHandler.Object);

        // Presumably I can create a Polly retry policy here, and add it to the HttpClient?
        // And then add a 2nd OK response and get rid of the try-catch?

        Uri substrateurl = new Uri("https://substrate.office.com/");
        try {
            await SIGSClient.Instance.PostAsync(client, substrateurl, new UserInfo(), "faketoken", new Signal(), Guid.NewGuid());
        }
        catch (SigsThrottledException e)
        {
            Assert.AreEqual(e.RetryAfterInSeconds, (uint)42);
        }
    }

I have a fair idea of how to create the Polly retry policy, but it seems all the unit test examples I can find expect that I use a HttpClientFactory to make the client, in which case I am not sure how to make THAT pump out the mock client.

Upvotes: 1

Views: 1437

Answers (1)

Anders Sewerin Johansen
Anders Sewerin Johansen

Reputation: 1666

There's no way that I can find to inject a policy of this kind into a HttpClient if HttpClientFactory instance, so you'll have to use it explicitly like in this example.

Upvotes: 0

Related Questions