unit test polly retry c# unit test polly retry c#

The Circuit Breaker pattern prevents an application from performing an operation that's likely to fail. Don't include object files that have a main function or another standard entry point such as wmain, WinMain, or DllMain. It is important to have the circuit working on a higher level than the call (i.e. When all retry attempts fail, it fails. Also, the shown code might not always show the best way to implementat things, it is just an example to explain some use cases of Polly. I am using Refit because it is quick and easy to use with REST APIs but Polly can be used with any kind of C# code. TL;DR: Configure a mock of the underlying system to return faults the policies should handle. How do you unit test LoggerMessage.Define() in .NET Core 3.1 with Moq? At first sight it may look as lost case, but things are not actually that bad. Maybe the API is spinning up, rebooting or there might be a network issue: But what if the API throws an exception because my access token is expired? Can my creature spell be countered if I cast a split second spell after it? In the DI container set the handler to be applied to the injected http client, this will be avalible to the constructor of FooService. retryAttempt => TimeSpan.FromSeconds(Math.Pow(retrySleepDuration, retryAttempt)), InlineData(1, HttpStatusCode.RequestTimeout), InlineData(0, HttpStatusCode.InternalServerError), GetRetryPolicy_Retries_Transient_And_NotFound_Http_Errors. No problem, glad it could help. An application can combine these two patterns. How can I unit test polly retry? See here You can configure these methods on a mock policy, to return or throw faults you want to simulate. We'll try using SystemClock in our unit tests. 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. I like the way you explain things, tell why, and offer alternatives. The class below implements this calculation: (1 second * 2^attemptCount-1) + random jitter between 10-200ms. 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. One of those classes is System.Net.HttpClient class. Did the drapes in old theatres actually say "ASBESTOS" on them? Queston 1: Am I missing something? How can Config be setup for Integration test within WithWebHostBuilder() in TestRetry() method if it is the correct method, and for unit test in HttpClientFactory_Polly_Policy_Test class. Find centralized, trusted content and collaborate around the technologies you use most. Polly policies all fulfil execution interfaces (ISyncPolicy, ISyncPolicy, IAsyncPolicy and IAsyncPolicy). 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. Disclaimer: this article and sample code have nothing to do with the work I did for the eCommerce website. I do like writing unit tests but especially when programming difficult scenarios with APIs and policies. There are still a lot of classes that we use daily in our code which we do not realize we cannot easily test until we get to writing unit tests for our existing code. Making statements based on opinion; back them up with references or personal experience. For example: it causes the policy to throw SocketException with a probability of 5% if enabled, For example: it causes the policy to return a bad request HttpResponseMessage with a probability of 5% if enabled. How my code behaves when the policy throws an exception, such as TimeoutRejectionException, BulkheadRejectedException or BrokenCircuitException. If there are going to be many concurrent requests, then it makes sense to use the exponential backoff with jitter strategy. Please view the original page on GitHub.com and not this indexable Asking for help, clarification, or responding to other answers. 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. So heres an example of writing a unit test for test scenario 2. Ideally when you need to mock something that is not and abstract class or interface you could always wrap it a class that implements interface which you could mock later. We use it so often to make web requests. Theres only one instance of Random, and there could be multiple threads making requests concurrently. Become a Patreon and get source code access: https://www.patreon.com/nickchapsasCheck out my courses: https://nickchapsas.comThe giveaway is now over. Thanks. Right-click on the solution node in Solution Explorer and choose Add > New Project on the shortcut menu to add the project template. How would I test what happens after we have re-tried 3 times? Now all client instances with name "sitemap" we use in our code will already have predefined base URL and retry policy configured by Polly. Unit testing retry policies with timeout intervals, http://www.introtorx.com/Content/v1.0.10621.0/16_TestingRx.html#TestScheduler. This only tests that a mock is being called, not that the retry policy is working. ErrorProneCode.cs is the unreliable class that I will mock and pass mocked policies into. The only difference is I made it randomly return the 429 error status code. (in response to "I cannot retrieve the HttpClient that has been configured with the Polly polly"), (to respond to the question title: "Test Polly retry polly configured via Startup.ConfigureServices() with ASP.NET Core API"). you directly to GitHub. C# - How to use Polly to do retries | MAKOLYTE rev2023.5.1.43404. I want to find out how Polly retry polly configured via Startup.ConfigureServices() can be tested. to your account. as GitHub blocks most GitHub Wikis from search engines. SystemClock.Sleep allows me to mock the internal timer for Polly, which causes the sleeps to really not sleep. Define and run unit tests inside one or more test projects. using Polly; using System; using System.Diagnostics; using System.Net.Cache; using System.Net.Http; public class RetryClient { private HttpClient httpClient = new HttpClient (new WebRequestHandler () { CachePolicy = new HttpRequestCachePolicy (HttpRequestCacheLevel.NoCacheNoStore) }); public HttpResponseMessage PostAsyncWithRetry ( String url, Asking for help, clarification, or responding to other answers. It also has options you can configure via Tools > Options. But, to allow you to concentrate on delivering your business value rather than reinventing Polly's test wheel, keep in mind that the Polly codebase tests its own operation extensively. You can download the Google Test adapter and Boost.Test Adapter extensions on the Visual Studio Marketplace. Let's see how our unit test for the controller method from above would look like. Note: You may have noticed this is checking HttpRequestException.StatusCode. Then you would know the retry had been invoked. I am getting answers right away here. In this simple example, I will demonstrate how to . Transient errors, by definition, are temporary and subsequent attempts should succeed. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? That is, it only sends request one time, not three times. That could be with a full DI container, or just simple constructor injection or property injection, per preference. Ubuntu won't accept my choice of password. But, to allow you to concentrate on delivering your business value rather than reinventing Polly's test wheel, keep in mind that the Polly codebase tests its own operation extensively. Finally, I want to verify that my code will work if no Polly policy is in use. This is what the flow will look like in code: And the unit test to test the full flow (check the repository on Github to see the mock setups): So now we have a retry and a fallback. It will authenticate first (the authentication service itself will also use Polly) and try to get products. When developing an application with Polly you will also probably want to write some unit tests. How do I test what my code does without Polly 'interfering'? rendering errors, broken links, and missing images. Published with Wowchemy the free, open source website builder that empowers creators. Polly is an awesome open source project part of the .Net Foundation. If it fails with a different exception or status code, it propagates the exception to the caller. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Most people just throw code at you and dont explain anything. Instead it inherits HttpMessageInvoker class. I also wasnt sure on the value of using async when its just a log, so I switched it out. For Boost.Test, see Boost Test library: The unit test framework. It will retry for a number of time when receiving any exception. There's a ton of other articles already. Lets try and implement the same scenario in a more clean and maintainable way by using Polly! To subscribe to this RSS feed, copy and paste this URL into your RSS reader. For more information on unit testing, see Unit test basics. This week I was connecting an eCommerce web application to an ERP system with REST APIs. privacy statement. It will retry up to 3 times. Where can I find a clear diagram of the SPECK algorithm? The indexable preview below may have If the test code doesn't export the functions that you want to test, add the output .obj or .lib files to the dependencies of the test project. Unit Testing retry policy with SqlExceptions #768 - Github What are the advantages of running a power tool on 240 V vs 120 V? Right-click on the failing test for a pop-up menu. Making statements based on opinion; back them up with references or personal experience. There are multiple endpoints, all authenticated with OAuth. In your test you recreate an alternative HttpClient + retry integration. Guess not! The circuit breaker keeps track of the number of exceptions. Retry & Circuit Breaker Patterns in C# with Polly Retry and circuit-breaker patterns are the 2 most common approaches when coding for resiliency. Can it still be improved? C# "internal" access modifier when doing unit testing. This means when the retry conditions are met, it retries the request. This will be my full AuthenticationService: Now I can test the behavior with Moq to mock the API: Let us dive a bit deeper into policies and Polly and combine different policies (and even add two more). If I configure Policy.Handle().Retry(3), it would be nice to check it really works, right? 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. Polly has many options and excels with it's circuit breaker mode and exception handling. .NET Core: Use HttpClientFactory and Polly to build rock solid services You can also explore and run the Polly-samples to see policies working individually, and in combination. 1. This can be simple, like hardcoding a delay time: You can use the attempt count in the calculation, like this: The most complex calculation is the exponential backoff with jitter strategy (Note: This is implemented in the HttpClient example section below). To learn more, see our tips on writing great answers. So, lets say hi to the circuit breaker. I guess I should be able to create an exact test but for demonstration purposes this will serve its purpose. There are no ads in this search engine enabler service. So, how does it test the integration between the HttpClient and the retry policy? When developing an application with Polly you will also probably want to write some unit tests. This is a great way how to easily implement retrials when using .NET Core dependency injection, but in case of using Autofac with .NET Framework 4.x you do not have many out of the box solutions. If that code expectation is not all wired up properly inside the app, it could be a cause of test failure. In addition, Ill show the exponential backoff with jitter calculator class. You may want to test how your code reacts to results or faults returned by an execution through Polly. Use CodeLens. C# Polly WaitAndRetry policy for function retry, Unit test Polly - Check whether the retry policy is triggered on timeout / error. For example, lets say youre implementing an algorithm to calculate predictions and its prone to transient errors. Assert.Equal (4, Add (2, 2)); } In order to skip a test (or fact) you need to pass in the skip parameter, followed by a reason why you decided to skip the test. 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). The test simply proves that HttpClientFactory does configure the HttpClient to use the policy. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. You signed in with another tab or 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. Lets say I have a micro service with an API endpoint to retrieve products: Could everything just be as simple as that. For more information on using Test Explorer, see Run unit tests with Test Explorer. Was Aristarchus the first to propose heliocentrism? In the following example, assume MyClass has a constructor that takes a std::string. Polly defines a NoOpPolicy for this scenario. Discover .NET - Polly After the final attempt, it stopped retrying and let the exception bubble up. Polly is a .NET resilience and transient-fault-handling library that allows developers to express policies such as Retry, Circuit Breaker, Timeout, Bulkhead Isolation, and Fallback in a fluent and thread-safe manner. using xunit and moq. In other words, it's a full end-to-end integration test. You can then use these values to sort and group tests in Test Explorer. Implement HTTP call retries with exponential backoff with Polly Testing Your Code When Using Polly | no dogma blog During the mock setup, it stores the Dequeue value as a return instead of invoking it every time. Its practically a guarantee that youll eventually run into some kind of transient error. The following sections show the basic steps to get you started with C++ unit testing. With HTTP requests, its not a question of if youll run into transient errors, but when. This is useful if you have many concurrent requests because it spreads out retry attempts. To produce a test result, use the static methods in the Assert class to test actual results against expected results. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. With both previous methods, we can use this retry logic in C# for both, Actionand Funcdelegates. Have a question about this project? A Software Engineer with a passion for quality, testing and sharing knowledge. Check out my Pluralsight course on it. Is there a generic term for these trajectories? This is (almost) the shortest xUnit test I could write that HttpClientFactory does correctly configure and use a policy. Has the Melford Hall manuscript poem "Whoso terms love a fire" been attributed to any poetDonne, Roe, or other? Retry and fallback policies in C# with Polly - Jacobs Blog 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. PolicyResult and PolicyResult have public factory methods, allowing you to mock .ExecuteAndCapture() overloads to return the PolicyResult of your choice. Thanks for your suggestions. Hi, Thanks. Polly is a .NET resilience and transient-fault-handling library that allows developers to express policies such as Retry, Circuit Breaker, Timeout, Bulkhead Isolation, Rate-limiting and Fallback in a fluent and thread-safe manner. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? Using an Ohm Meter to test for bonding of a subpanel. When theres an error, it retries, and then succeeds 3. 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. 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. On the Test menu, choose Windows > Test Explorer. Edit and build your test project or solution. The unit test itself does not look so sophisticated as it would be as if you would wrap HttpClient class to implementation of an interface, but this way you get to keep using IHttpClientFactorywhich is more beneficial for your application than adapting it to much to have simpler unit tests. A test adapter integrates unit tests with the Test Explorer window. Visual Studio includes these C++ test frameworks with no extra downloads required: You can use the installed frameworks, or write your own test adapter for whatever framework you want to use within Visual Studio. GitHub blocks most GitHub Wikis from search engines. There are many possible HTTP transient errors. Has the Melford Hall manuscript poem "Whoso terms love a fire" been attributed to any poetDonne, Roe, or other? Test Polly retry polly configured via Startup - Github Want to learn more about Polly? Implementing the Circuit Breaker pattern | Microsoft Learn How to Implement Retry Logic in C# - Code Maze URL: https://github.com/App-vNext/Polly/wiki/Unit-testing-with-Polly. But how can we verify all these scenarios work? 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. Lets try and create a unit test to test the behavior of the circuit breaker. Adding Polly retry policy to a mocked HttpClient? The .cpp file in your test project has a stub class and method defined for you. This retry policy means when an exception of type TransientException is caught, it will delay 1 second and then retry. Example: Thanks for contributing an answer to Stack Overflow! There is no need for any WebApplicationFactory, IHost, IHostedService or anything from ASP.NET. I think most of us, at some point in time, we saw code like this, trying to implement some kind of retry logic. You can use the onRetry method to try to fix the problem before the next retry attempt. This example shows how you can test that the constructor initializes the class the way you expect: In the previous example, the result of the Assert::AreEqual call determines whether the test passes or fails. Hi @PingPongSet . It works just like it does for other languages. It has a project template that you can add to a solution. Create the projects in the same solution as the code you want to test. Mocking HttpClient in unit tests with Moq and Xunit when using IHttpClientFactory, Mocking System.IO filesystem in unit tests in ASP.NET Core, Increase service resilience using Polly and retry pattern in ASP.NET Core. I want to unit test a polly retry logic. A TEST_METHOD returns void. You should only retry if the attempt has a chance of succeeding. So, lets add some simple retry (this is kind of pseudo-code, just for demonstration purpose): Although it is not the most beautiful code, it might actually work for you. The app-under-test in their sample app is also using typed-clients from IHttpClientFactory; and is also using WebApplicationFactory to orchestrate the tests; so is a close fit for the test approach you have already started on. TL;DR Mock your policies to return or throw particular outcomes, to test how your code responds. When the configured delay time has been passed it will reset the circuit and start all over. With Polly it is possible to create complex and advanced scenarios for error handling with just a few lines of code. Repeat for any more headers. @reisenberger I agree with @jiimaho in that there should be a supported way to manipulate the passage of time. It should be easy to expand this sample to test more sophisticated policies, for example to test .SetWaitAndRetryPolicy1(). This integration can be tested via an integration or component test. To avoid having to type the full path in each include statement in the source file, add the required folders in Project > Properties > C/C++ > General > Additional Include Directories. Why do men's bikes have high bars where you can hit your testicles while women's bikes have the bar much lower? In the DI container set the handler to be applied to the injected http client, this will be avalible to the constructor of FooService. I added the circuit breaker to the order service: All unit tests will still succeed because the circuit breaker will only break after 10 exceptions. So, this code does not test any part of the original code. In your test code, inject an equivalent policy that doesn't do any waiting, eg. C# - Retry Pattern with Polly - Code4Noobz This angle on testing aims to check you've configured policies to match your desired resilience behaviour. Readme Issues Note Important Announcement: Architectural changes in v8 Please tell me if you have started using Polly. This can be facilitated by using dependency injection to pass policies into code. If any of your tests are missing from the window, build the test project by right-clicking its node in Solution Explorer and choosing Build or Rebuild. 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. Additionally, we want to be able to make our methods that rely on Polly unit testable. using AutoFixture . I closed the my issue as it's not relevant anymore. In this case, the policy is configured to try six times with an exponential retry, starting at two seconds. When you retry without a delay, it means youll be changing something that should fix the problem so that the retries succeed. Thoughts/questions about unit-testing? It will open the circuit for a certain amount of time which means it will not even try to execute the call but immediately throw an exception. Let's say you use the following approach, and this code below is part of your method that does a few more things than executing the policy itself. Choose Debug to step through the function where the failure occurred. Use DI to provide policies to consuming classes; tests can then stub out Polly by injecting NoOpPolicy in place of real policies. It will retry up to 3 times. Connect and share knowledge within a single location that is structured and easy to search. For more information on unit testing, see Unit test basics. Notice the last line. 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. Which was the first Sci-Fi story to predict obnoxious "robo calls"? How to unit test retry policy, First, theres three primary scenarios to verify: 1. For examples taking this concept further with PolicyRegistry or a policy factory, see our Unit testing with examples page. TEST_CLASS and TEST_METHOD are part of the Microsoft Native Test Framework. preview if you intend to use this content. In this article, Ill go into more details about how to use Polly to do retries. Lets say you want to check if your code was retried 3 times and then successfully completed on the final attempt. The button and/or link above will take Why are players required to record the moves in World Championship Classical games? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. It was just a trigger for me to write about Polly. In this section, Ill only try to handle one: the Too Many Requests error response (429). Suggested strategy: stub out Polly for the purposes of those tests. 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. How to add clean Retrying in .NET Core using Polly - YouTube When you use code like this in a production environment you will quickly find out that there is a need of exception handling. Updated Integration Test method In addition, it creates and contains the AsyncRetryPolicy (Note: You could pass it in instead). For this kind of scenarios there is a very cool library: Polly which I have been using for some years now (together with Refit) and I am just deeply in love with both libraries. I cannot retrieve the HttpClient that has been configured with the Polly polly. I posted the same question on StackOverflow a few weeks ago without any answer. Write unit tests for C/C++ - Visual Studio (Windows) 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. Example if GET /person/1 responded in 404 it COULD mean 1 doesnt exist but the resource is still there. Question 2: The following illustration shows a test project whose tests have not yet run. Initialize CodeLens for a C++ unit test project in any of the following ways: Edit and build your test project or . I hope you did learn something here. HTTP Retry with Polly | Carl Paton | There are no silly questions A common need is to test the logic of your system-under-test as if Polly were not part of the mix. Refactor to inject the Policy into the method/class using it (whether by constructor/property/method-parameter injection - doesn't matter).