result.StatusCode.Should().Be(expectedHttpStatusCode); https://www.stevejgordon.co.uk/polly-using-context-to-obtain-retry-count-diagnostics, https://github.com/App-vNext/Polly/issues/505, https://github.com/App-vNext/Polly/wiki/Polly-and-HttpClientFactory#use-case-exchanging-information-between-policy-execution-and-calling-code, injected HttpClient with mocked out http responses, Implement HTTP call retries with exponential backoff with IHttpClientFactory and Polly policies, https://www.thecodebuzz.com/httpclient-resiliency-http-polly-csharp-netcore/, https://josephwoodward.co.uk/2020/07/integration-testing-polly-policies-httpclient-interception, https://anthonygiretti.com/2019/03/26/best-practices-with-httpclient-and-retry-policies-with-polly-in-net-core-2-part-2/, https://nodogmablog.bryanhogan.net/2019/03/testing-your-code-when-using-polly/, TCP Socket Action Probe In Worker (Liveness), 2nd => HttpStatusCode.RequestTimeout (408), 1st => HttpStatusCode.InternalServerError (500). Ubuntu won't accept my choice of password. Lets extend it a bit. Not the answer you're looking for? Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? Adding Polly retry policy to a mocked HttpClient? The only difference is I made it randomly return the 429 error status code. To test that the retry policy is invoked, you could make the test setup configure a fake/mock ILog implementation, and (for example) assert that the expected call .Error("Delaying for {delay}ms, ") in your onRetry delegate is made on the fake logger. Let us know how you get on with that - or if you can envisage ways it could be improved (I can envisage some - as ever, with trade-offs). Adding Polly retry policy to a mocked HttpClient? Per my original post, if you just want a tight unit-test on the HttpClient "test" configured via HttpClientFactory, you can also do this with the "shortest-possible approach", without needing to involve WebApplicationFactory. Using an Ohm Meter to test for bonding of a subpanel. I want an advanced scenario that looks like this: I will not implement authentication in this flow but I guess you can already imagine: a) the flow will be much more complicated, b) it will still be quite easy to implement with Polly using the example from above. Visual Studio 2017 and later (Professional and Enterprise editions). With both previous methods, we can use this retry logic in C# for both, Actionand Funcdelegates. That is, it only sends request one time, not three times. privacy statement. When you retry with a delay, it means you think the the transient error will go away by itself after a short period of time. In case of unit testing you are not relying on your DI. Then you would know the retry had been invoked. Published with Wowchemy the free, open source website builder that empowers creators. One of these classes come from namespace System.IO for file and folder operations, but luckily there are libraries that help you write testable code using System.IO classes. Do all the tests need adjusting? CTest support is included with the C++ CMake tools component, which is part of the Desktop development with C++ workload. Become a Patreon and get source code access: https://www.patreon.com/nickchapsasCheck out my courses: https://nickchapsas.comThe giveaway is now over. github.com/justeat/httpclient-interception, How a top-ranked engineering school reimagined CS curriculum (Ep. The code is simple, it hardly needs further explanation. This angle on testing aims to check you've configured policies to match your desired resilience behaviour. During the mock setup, it stores the Dequeue value as a return instead of invoking it every time. Right-click on the failing test for a pop-up menu. A TEST_METHOD returns void. When you retry without a delay, it means youll be changing something that should fix the problem so that the retries succeed. In the Add Reference dialog, choose the project(s) you want to test. Find centralized, trusted content and collaborate around the technologies you use most. It has helped me a lot today, github.com/App-vNext/Polly/blob/master/src/Polly.SharedSpecs/, How a top-ranked engineering school reimagined CS curriculum (Ep. @reisenberger I think it's good to let consumers of the Polly API be able to provide a time-provider. Where can I find a clear diagram of the SPECK algorithm? .NET Core has done a great job by introducing interface for most of classes which makes them easy to write unit tests around them. Asking for help, clarification, or responding to other answers. A simple retry will not be enough because what if the order api is offline for a longer time? For more information, see How to: Use Boost.Test in Visual Studio. PolicyResult and PolicyResult have public factory methods, allowing you to mock .ExecuteAndCapture() overloads to return the PolicyResult of your choice. You can then use these values to sort and group tests in Test Explorer. In this example, Im using the following service stub that randomly returns the Too Many Requests (status code 429) error response: Note: This is the WeatherForecastController class that Visual Studio auto-generates for you when you use the ASP.NET Web API template. Right-click on the test project node in Solution Explorer for a pop-up menu. I Honestly love this approach, thanks for the article, this was really helpful, i was able to get a simple retry working using this. From version 6.0.1, Polly targets .NET Standard 1.1 and 2.0+. Has the Melford Hall manuscript poem "Whoso terms love a fire" been attributed to any poetDonne, Roe, or other? When theres no errors, it succeeds and does no retries 2. Use CodeLens. privacy statement. http://www.introtorx.com/Content/v1.0.10621.0/16_TestingRx.html#TestScheduler for more information. A test adapter integrates unit tests with the Test Explorer window. Create the retry policy. Google Test Adapter is included as a default component of the Desktop development with C++ workload. With Polly, you can define a Retry policy with the number of retries, the exponential backoff configuration, and the actions to take when there's an HTTP exception, such as logging the error. I offer this variant in case you just want the shortest possible test of the functionality declared in a method like .SetWaitAndRetryPolicy1(). Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Thoughts/questions about unit-testing? retryAttempt => TimeSpan.FromSeconds(Math.Pow(retrySleepDuration, retryAttempt)), InlineData(1, HttpStatusCode.RequestTimeout), InlineData(0, HttpStatusCode.InternalServerError), GetRetryPolicy_Retries_Transient_And_NotFound_Http_Errors. While this is not a complete solution it can already handle some issues. In this article, Ill go into more details about how to use Polly to do retries. Embedded hyperlinks in a thesis or research paper. Imagine this: I want a retry on the authentication api but only when I receive a RequestTimeout (Http status code 408). It has nothing to do with caching. No problem, glad it could help. The class below implements this calculation: (1 second * 2^attemptCount-1) + random jitter between 10-200ms. This class is passed into the client so it can be used as the sleepDurationProvider Polly parameter. Boolean algebra of the lattice of subspaces of a vector space? Several third-party adapters are available on the Visual Studio Marketplace. Imagine the order api is really broken. Last Modified: Mon, 23 Sep 2019 21:54:42 GMT, This page is a concise conceptual overview of different unit-testing approaches you may take with Polly. The button and/or link above will take For more information, see How to: Use CTest in Visual Studio. At first sight it may look as lost case, but things are not actually that bad. I do like writing unit tests but especially when programming difficult scenarios with APIs and policies. This means every outbound call that the named-client "test" makes would return HttpStatusCode.InternalServerError; it's a minimal example of what HttpClientInterception does, but HttpClientInterception does more, does it with much more configurability, and with a nice fluent syntax. Boost.Test requires that you manually create a test project. Why did DOS-based Windows require HIMEM.SYS to boot? To add a new test project to an existing solution. Initialize CodeLens for a C++ unit test project in any of the following ways: After it's initialized, you can see the test status icons above each unit test. How a simple API call can get way too complex There is no need for any WebApplicationFactory, IHost, IHostedService or anything from ASP.NET. TL:DR; Polly's NoOpPolicy allows you to stub out Polly, to test your code as if Polly were not in the mix. In your test you recreate an alternative HttpClient + retry integration. Because WebApplicationFactory.CreateClient() has no overloads that returns the named HttpClient: Update After Comment from @reisenberger 4 Jan 2019. How to verify that method was NOT called in Moq? Updated Integration Test method What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? In the next case I verify that the application has correctly used the retry policy method. Guess not! I don't want to wait more than one minute in my tests. I updated my existing integration test method to below, but the retry policy is not activated. But how can we verify all these scenarios work? To enable access to the functions in the project under test, add a reference to the project in your test project. After adding some logging to the service and creating the unit test I got this log result: The unit test is a bit funny. Note: You may have noticed this is checking HttpRequestException.StatusCode. in order to trigger Polly's fault and resilience policies such as WaitAndRetry. This is (almost) the shortest xUnit test I could write that HttpClientFactory does correctly configure and use a policy. In your test code, inject an equivalent policy that doesn't do any waiting, eg Retry (3) // etc Extract static SystemClock to interface So for the test to succeed, your app must be configured such that invoking the http://localhost:1234/api/v1/car/ endpoint eventually chains on internally to something (via HttpClientService?) How does having the Polly policy in play affect your existing unit tests? How my code behaves when the policy throws an exception, such as TimeoutRejectionException, BulkheadRejectedException or BrokenCircuitException. I'm trying to write a unit test for polly, but it looks like the return is cached. rev2023.5.1.43404. You signed in with another tab or window. Which language's style guidelines should be used when writing code that is supposed to be called from another language? Boost.Test is included as a default component of the Desktop development with C++ workload. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Hi, There is a nice way to test these type of scenario using Http interceptions - using JustEat nuget, checkthis out ->. In Test Explorer, choose Run All, or select the specific tests you want to run. Can my creature spell be countered if I cast a split second spell after it? If you want to test the Polly policy configured on IHttpClientService within your app, via an end-to-end integration test of your app orchestrated by WebApplicationFactory, then you will have to fire the whole request at http://localhost:1234/api/v1/car/ (as your test code is already doing), and somehow stub out whatever downstream call http://localhost:1234/api/v1/car/ is making through HttpClientService. Edit and build your test project or solution. To add a new test project to an existing solution. It was just a trigger for me to write about Polly. This is useful if you have many concurrent requests because it spreads out retry attempts. Writing unit-tests to verify that Polly works can be a very valuable way to explore and understand what Polly does. So, this code does not test any part of the original code. Thanks. If you want to know more of how to easily retry and make your application more resilient to poor and unstable network connection check articleIncrease service resilience using Polly and retry pattern in ASP.NET Core. For failed tests, the message displays details that help to diagnose the cause. you directly to GitHub. Although there are abundant resources about Polly on the web I wanted to write a post with a lot of sample code to provide a quick and practical example of how easy it is to use Polly to create advanced exception handling with APIs. I closed the my issue as it's not relevant anymore. There are many possible HTTP transient errors. SystemClock.Sleep allows me to mock the internal timer for Polly, which causes the sleeps to really not sleep. I cannot retrieve the HttpClient that has been configured with the Polly polly. The test uses WebApplicationFactory to exercise your normal app startup in configuring the HttpClient/policy to be tested; but then pull the "test" HttpClient configuration out for a tighter unit test. EDIT: Improved the Unit-testing wiki to highlight this. If you want to know more about mocking System.IO classes you can checkoutMocking System.IO filesystem in unit tests in ASP.NET Core article. This means when the retry conditions are met, it retries the request. The microsoft example also sets .SetHandlerLifetime (TimeSpan.FromMinutes (5)). Ill show the client and service (stubbed to return the error response) code below and the results of running it. Changing it to () => responses.Dequeue() works now. How do you unit test LoggerMessage.Define() in .NET Core 3.1 with Moq? The basic configuration is similar for both the Microsoft and Google Test frameworks. really helpful. Now all client instances with name "sitemap" we use in our code will already have predefined base URL and retry policy configured by Polly. Sign in To test that the retry policy is invoked, you could make the test setup configure a fake/mock ILog implementation, and (for example) assert that the expected call .Error ("Delaying for {delay}ms, .") in your onRetry delegate is made on the fake logger. Why are players required to record the moves in World Championship Classical games? appsettings.json). In this section, Ill only try to handle one: the Too Many Requests error response (429). Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Connect and share knowledge within a single location that is structured and easy to search. As suggested in the comments I recommend Simmy. Finally, I want to verify that my code will work if no Polly policy is in use. Setting upIHttpClientFactory is quite easy in ASP.NET Core container setup in Startup.cs. For example, lets say you want to log retry information: The sleepDurationProvider parameter allows you to pass in a lambda to control how long itll delay before doing a retry. For more information about using Test Explorer, see Run unit tests with Test Explorer. Why did US v. Assange skip the court of appeal? Well occasionally send you account related emails. On retry attempts, you want to change the parameters to reduce the chances of transient errors during the next retry attempt: Note: The Fallback policy might have been a good option here, but the purpose of this is to show how to do retries without delaying. The Polly policy is configured within the test. In the DI container set the handler to be applied to the injected http client, this will be avalible to the constructor of FooService. In the following example, assume MyClass has a constructor that takes a std::string. Define and run tests inside one or more test projects. Polly has many options and excels with it's circuit breaker mode and exception handling. Too me, this is one of the most important (and fun) parts. Sign in 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Most people just throw code at you and dont explain anything. We can include 404 (Not Found) but that depends on the use case, in some APIs 404 means the data you were looking for is not avalible. If you check the constructor of HttpClient you will see that it inherits and abstract class IHttpMessageHandler which can be mocked since it is an abstract class. Define and run unit tests inside one or more test projects. See these example links: 1; 2; 3; 4. I am using polly to handle retry (see below code). There are no ads in this search engine enabler service. The WeatherClient contains this single HttpClient instance. Yes, it can! At the end, Ill show a full example of retrying HttpClient requests with Polly. Have a question about this project? You can use the onRetry method to try to fix the problem before the next retry attempt. Example if GET /person/1 responded in 404 it COULD mean 1 doesnt exist but the resource is still there. How can I unit test polly retry? Writing unit-tests to verify that Polly works can be a very valuable way to explore and understand what Polly does. Can it still be improved? For more information on unit testing, see Unit test basics. The .cpp file in your test project has a stub class and method defined for you. Test Polly retry polly configured via Startup.ConfigureServices() with ASP.NET Core API. What are the advantages of running a power tool on 240 V vs 120 V? I posted the same question on StackOverflow a few weeks ago without any answer. GitHub blocks most GitHub Wikis from search engines. This makes it like a half-integration, half-unit test. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? This can be done with a simple DummyMethod that keeps track of its invocations and has a sorted and predefined collection of response http status codes. However, if you intended the test to exercise more directly the "test" configuration from HttpClientFactory, you may want: so that the variable client is assigned the "test" configuration from HttpClientFactory.