unit test polly retry c#

To subscribe to this RSS feed, copy and paste this URL into your RSS reader. If there are going to be many concurrent requests, then it makes sense to use the exponential backoff with jitter strategy. Not sure why, but it looks like the responses queue is only being Dequeue once, this leads me to believe the response is being cache. Unit testing retry policies with timeout intervals, http://www.introtorx.com/Content/v1.0.10621.0/16_TestingRx.html#TestScheduler. When all retry attempts fail, it fails. Repeat for any more headers. Thanks for your suggestions. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Polly is able to wrap different policies to handle different scenarios: While this is not the way I would structure my code in a real app, I believe this is understandable and maintainable code. Here's an example from an blockchain challenge I had to do, I execute 4 calls in a row, so if the InjectionRate is 0.25 one of the 4 calls would trigger a Polly policy: You can unit test this by mocking out the HttpClient and setting up your own test version of the WaitAndRetryAsync policy. For . Disclaimer: this article and sample code have nothing to do with the work I did for the eCommerce website. A common need is to test the logic of your system-under-test as if Polly were not part of the mix. Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? Was Aristarchus the first to propose heliocentrism? Write unit tests for C/C++ - Visual Studio (Windows) I do like writing unit tests but especially when programming difficult scenarios with APIs and policies. Queston 1: Am I missing something? What my code should do if there was no policy in place. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? 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. Simply set the InjectionRate to 1 to guarantee a fault in your unit test. 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. to your account. Published with Wowchemy the free, open source website builder that empowers creators. c# - Testing Polly retry policy with moq - Stack Overflow 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. Generating points along line with specifying the origin of point generation in QGIS, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A). The .cpp file in your test project has a stub class and method defined for you. If this should be done through SystemClockor not i'm not sure, however in our scenario it's perfect for testability. Before we jump to an actual problem of writing a test for IHttpClientFactory and HttpClient which instance is create by IHttpClientFactory, let's see how the actual setup looks like in Startup.cs class file. 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). Right-click on the solution node in Solution Explorer and choose Add > New Project on the shortcut menu to add the project template. Retry & Circuit Breaker Patterns in C# with Polly Retry and circuit-breaker patterns are the 2 most common approaches when coding for resiliency. ErrorProneCode.cs is the unreliable class that I will mock and pass mocked policies into. In your tests, inject NoOpPolicy rather than the policies you use in production, and Polly is stubbed out of those tests. Does a password policy with a restriction of repeated characters increase security? Using the Executor Class Once we have defined the Executorclass and its methods, it is time to execute the FirstSimulationMethodand the SecondSimulationMethodmethods. 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. Running this outputs the following: 03:22:26.56244 Attempt 1 03:22:27.58430 Attempt 2 03:22:28.58729 Attempt 3 03:22:29.59790 Attempt 4 Unhandled exception. You can also explore and run the Polly-samples to see policies working individually, and in combination. I want to unit test a polly retry logic. privacy statement. This is useful if you have many concurrent requests because it spreads out retry attempts. Polly is an awesome open source project part of the .Net Foundation. Test Polly retry polly configured via Startup - Github Can my creature spell be countered if I cast a split second spell after it? A good example of a library which allows the user to modify the flow of time is the ReactiveExtensions project. Alternatively, you could write your own very short StubDelegatingHandler. After adding some logging to the service and creating the unit test I got this log result: The unit test is a bit funny. Define and run unit tests inside one or more test projects. 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. 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. Right-click on the test project node in Solution Explorer for a pop-up menu. Choose the icon for more information, or to run or debug the unit test: More info about Internet Explorer and Microsoft Edge, To link the tests to the object or library files, Microsoft.VisualStudio.TestTools.CppUnitTestFramework API reference, Boost Test library: The unit test framework. Imagine the order api is really broken. HttpClient relies on the HttpMessageHandler.SendAsync method, so we can mock this method and class and pass it to the constructor or HttpClient class instance. Therefore, the call to Random.Next() has to be locked. 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. I updated my existing integration test method to below, but the retry policy is not activated. It will retry for a number of time when receiving any exception. The signatures use the TEST_CLASS and TEST_METHOD macros, which make the methods discoverable from the Test Explorer window. If that code expectation is not all wired up properly inside the app, it could be a cause of test failure. That is, it only sends request one time, not three times. Also, tell me if you happen to know alternative libraries, I would very much like that! To do this, I pass in a NoOp policy. That is, it only sends request one time, not three times. When theres an error, it retries, and then succeeds 3. You can configure these methods on a mock policy, to return or throw faults you want to simulate. With Polly it is possible to create complex and advanced scenarios for error handling with just a few lines of code. For more information, see How to: Use Boost.Test in Visual Studio. Well occasionally send you account related emails. Making statements based on opinion; back them up with references or personal experience. TL:DR; Polly's NoOpPolicy allows you to stub out Polly, to test your code as if Polly were not in the mix. I like the way you explain things, tell why, and offer alternatives. [TestMethod()] public void TestProcessor_WhenError_Retries() { //arrange var mockProcessor = new Mock(); mockProcessor.SetupSequence(p => p.Process()) .Throws() //1st attempt .Throws() //retry 1 .Throws() //retry 2 .Pass(); //retry 3 succeeds (note: it's a void method, hence Pass() instead of Returns()). For failed tests, the message displays details that help to diagnose the cause. Check out my Pluralsight course on it. Example: Thanks for contributing an answer to Stack Overflow! To enable access to the functions in the project under test, add a reference to the project in your test project. I want to add a delay when I receive a timeout. That's exactly the way we handle it within Polly's own specs, to allow tests to run instantly where time-delays are involved: specs either substitute SystemClock.UtcNow or SystemClock.Sleep , depending on whether the policy-under-test is waiting passively for time to pass elsewhere (as in CircuitBreaker moving to half-open) or actively controlling the delay (as in WaitAndRetry). 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. Retry setting is set via a config file in JSON (e.g. If you write your own integration tests around policies in your project, note the possibility to manipulate Polly's abstracted SystemClock. You can add traits to test methods to specify test owners, priority, and other information. Find them at Test adapter for Boost.Test and Test adapter for Google Test. A test project creates a separate app that calls the code in your executable and reports on its behavior. For more information about using Test Explorer, see Run unit tests with Test Explorer. Test Explorer discovers test methods in other supported frameworks in a similar way. I cannot retrieve the HttpClient that has been configured with the Polly polly. The Circuit Breaker pattern prevents an application from performing an operation that's likely to fail. The "Retry pattern" enables an application to retry an operation in the expectation that the operation will eventually succeed. TL:DR; Bear in mind the Polly codebase already tests this for you extensively. Have a question about this project? Since it is an interface it is easy to mock it for the class constructors, but when it comes to actual unit tests we need to mock HttpClient class instance. This can be facilitated by using dependency injection to pass policies into code. We do not want to loose any order because this will directly result in money loss. In your production code, inject the real policy you want to use. In your test code, inject an equivalent policy that doesn't do any waiting, eg. to your account. While this is not a complete solution it can already handle some issues. That could be with a full DI container, or just simple constructor injection or property injection, per preference. This is a simple implementation of a retry method. These interfaces describe the .Execute/Async() overloads available on policies. In your production code, inject the real policy you want to use. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. On the Test menu, choose Windows > Test Explorer. means the variable HttpClient client which the test posts on (await client.PostAsync(url, content);) is assigned the HttpClient returned from WebApplicationFactory, the HttpClient instance designed to invoke your webapp, not the "test" configuration from HttpClientFactory. Changing it to () => responses.Dequeue() works now. Post an issue on the issues board. A test adapter integrates unit tests with the Test Explorer window. This is more general ASP.NET Core support rather than Polly, but some pointers: Options.Create<>() if you want the options to be entirely self-generated by a purely self-contained unit test; or use ConfigurationBuilder to read in external config (eg json settings file) if you want a more integration-style approach which reads in some version of your app's configuration. Most people just throw code at you and dont explain anything. It's integrated with Test Explorer, but currently doesn't have a project template. How my code behaves when a policy becomes active and changes the outcome of a call, such as when an unreliable request works because Polly performs a retry. When sending concurrent requests with HttpClient, its a good idea to use the same instance repeatedly. I have another question on setting system clock. It has nothing to do with caching. This property was added in .NET 5 (finally!). Please refer to my updated comments at the bottom of OP. SystemClock.Sleep allows me to mock the internal timer for Polly, which causes the sleeps to really not sleep. :). C# Polly WaitAndRetry policy for function retry, Unit test Polly - Check whether the retry policy is triggered on timeout / error. To add a new test project to an existing solution. Install nuget Microsoft.Extensions.Http.Polly. To show the results, I executed the following code several times to produce different output: Sometimes the server will return errors on every request attempt, and itll error out after 3 retry attempts: Other times itll retry a few times and then succeed: Note: I called WeatherClient.GetWeather() in a console app to produce these results. Why do men's bikes have high bars where you can hit your testicles while women's bikes have the bar much lower? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The Polly policy is configured within the test. If somebody changes the configuration, the test provides regression value by failing. Making statements based on opinion; back them up with references or personal experience. Next, in your unit test .cpp file, add an #include directive for any header files that declare the types and functions you want to test. After the final attempt, it stopped retrying and let the exception bubble up. I should add another retry around the retrieval of the access token, handle more cases in the switch statement, in short, this simple API is becoming an unmaintainable mess. Where can I find a clear diagram of the SPECK algorithm? To learn more, see our tips on writing great answers. In .NET Core we got IHttpClientFactory which allows us to have multiple configurations for HttpClient instances so that we do not need to repeat client setup. In case of unit testing you are not relying on your DI. Too me, this is one of the most important (and fun) parts. The microsoft example also sets .SetHandlerLifetime (TimeSpan.FromMinutes (5)). In your test you recreate an alternative HttpClient + retry integration. For more information on unit testing, see Unit test basics. Lets try and create a unit test to test the behavior of the circuit breaker. The test simply proves that HttpClientFactory does configure the HttpClient to use the policy. 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. Here are the scenarios I test for - How my code behaves when the policy throws an exception, such as TimeoutRejectionException, BulkheadRejectedException or BrokenCircuitException. Suggested strategy: stub out Polly for the purposes of those tests. The simplest way to check how many times code was executed is by using a mock. To do this, it can be helpful to mock your Polly policy to return particular results or throw particular outcomes on execution. See the many tests within the existing codebase which do this. Going further and checking HttpMessageInvoker, you can see that it is not an abstract class nor it implements any interface other than IDisposable which is not much helpful for us in this case since we need to mock behaviors id GetStringAsync method which does not come from IDisposable.

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