unit test polly retry c#
In the DI container set the handler to be applied to the injected http client, this will be avalible to the constructor of FooService. Notice the last line. 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. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? 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. 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. rendering errors, broken links, and missing images. How to unit test retry policy, First, theres three primary scenarios to verify: 1. Hi @PingPongSet . I figured it out. The microsoft example also sets .SetHandlerLifetime(TimeSpan.FromMinutes(5)). Because WebApplicationFactory.CreateClient() has no overloads that returns the named HttpClient: Update After Comment from @reisenberger 4 Jan 2019. With HTTP requests, its not a question of if youll run into transient errors, but when. 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. Updated Integration Test method First you create a retry policy, and then you use it to execute the error prone code: This retry policy means when an exception of type TransientException is caught, it will delay 1 second and then retry. To learn more, see our tips on writing great answers. The ability to manipulate Pollys abstracted, ambient-context SystemClock is intended to provide exactly this: you can manipulate time so that tests which would otherwise incur a time delay, dont. you directly to GitHub. Most people just throw code at you and dont explain anything. It should be easy to expand this sample to test more sophisticated policies, for example to test .SetWaitAndRetryPolicy1(). Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I have a few classes to demonstrate these scenarios, BusinessLogic.cs and OtherBusinessLogic.cs are the classes under test. 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. He also rips off an arm to use as a sword, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A). So heres an example of writing a unit test for test scenario 2. 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. Sign in 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. When you retry without a delay, it means youll be changing something that should fix the problem so that the retries succeed. to your account. The test simply proves that HttpClientFactory does configure the HttpClient to use the policy. A test project creates a separate app that calls the code in your executable and reports on its behavior. This week I was connecting an eCommerce web application to an ERP system with REST APIs. 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. Generic Doubly-Linked-Lists C implementation. Using the Executor Class Once we have defined the Executorclass and its methods, it is time to execute the FirstSimulationMethodand the SecondSimulationMethodmethods. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? This retry policy means when an exception of type TransientException is caught, it will delay 1 second and then retry. @reisenberger I agree with @jiimaho in that there should be a supported way to manipulate the passage of time. Install nuget Microsoft.Extensions.Http.Polly. Right-click on a test for other options, including running it in debug mode with breakpoints enabled. Of course, you could make StubDelegatingHandler more sophisticated, to return the error only 2 times or whatever. 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. 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). Where can I find a clear diagram of the SPECK algorithm? (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"). It must be manually configured. Why do men's bikes have high bars where you can hit your testicles while women's bikes have the bar much lower? 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. Repeat for any more headers. While this is not a complete solution it can already handle some issues. 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. This will be a different type of exception and it will also need a different solution to solve the problem. You may want to test how your code reacts to results or faults returned by an execution through Polly. If we got to HttpClient class definition you will see that it does not implement any interface we can mock. However, there are a lot of classes that re commonly used which are not refactored in .NET Core. In this blog I will try to explain how one can create clean and effective policies to retry API calls and have fallbacks when requests are failing. 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. Making statements based on opinion; back them up with references or personal experience. 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). Find them at Test adapter for Boost.Test and Test adapter for Google Test. For examples taking this concept further with PolicyRegistry or a policy factory, see our Unit testing with examples page. Thanks. From version 6.0.1, Polly targets .NET Standard 1.1 and 2.0+. We'll try using SystemClock in our unit tests. Transient errors, by definition, are temporary and subsequent attempts should succeed. You can use the onRetry method to try to fix the problem before the next retry attempt. Finally, I want to verify that my code will work if no Polly policy is in use. The Assert class contains many other methods to compare expected results with actual results. 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. 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. Question 2: There is no need for any WebApplicationFactory, IHost, IHostedService or anything from ASP.NET. Do we want customer to have a slower experience while retrying to reach the API although we know the last few calls have been unsuccessful? 1. Finally, it executes the requests with HttpClient with the retry policy. For more information about using Test Explorer, see Run unit tests with Test Explorer. It has a project template that you can add to a solution. You can download the Google Test adapter and Boost.Test Adapter extensions on the Visual Studio Marketplace. I'm trying to write a unit test for polly, but it looks like the return is cached. Let's check it: Executor.Execute(FirstSimulationMethod, 3); Imagine the order api is really broken. From the Polly repository: 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. When theres an error, it retries, and then succeeds 3. For more information on unit testing, see Unit test basics. About GitHub Wiki SEE, a search engine enabler for GitHub Wikis In this testing approach, you typically stub or mock out the underlying systems called (for instance you might stub out a call to some endpoint to return TimeoutException), then check your configured policy does handle that. Visual Studio 2017 and later (Professional and Enterprise editions). Thanks for that @rog1039 . There are no ads in this search engine enabler service. 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. There's a ton of other articles already. See here They provide schedulers that can be used control the flow of time which makes testing various scenarios relating to time passage very easy, repeatable, and makes unit tests very quick (Can simulate minute/hours/days/etc of time passage instantly). The simplest way to check how many times code was executed is by using a mock. With Polly it is possible to create complex and advanced scenarios for error handling with just a few lines of code. Can it still be improved? What my code should do if there was no policy in place. C# Quicktip: In Xunit how to skip a unit test from being run A simple retry will not be enough because what if the order api is offline for a longer time? You can do retries with and without delays. 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 ->. This makes it like a half-integration, half-unit test. preview if you intend to use this content. The Retry Pattern allows us to retry a task in case of exceptions, can put a delay between these retries, can manage timeout, etc. In the DI container set the handler to be applied to the injected http client, this will be avalible to the constructor of FooService. Google Test Adapter is included as a default component of the Desktop development with C++ workload. as GitHub blocks most GitHub Wikis from search engines. C# Polly WaitAndRetry policy for function retry, Unit test Polly - Check whether the retry policy is triggered on timeout / error. 2023 Jacob Duijzer. Some transient errors can be fixed by delaying for a short time. At first sight it may look as lost case, but things are not actually that bad. preview if you intend to, Click / TAP HERE TO View Page on GitHub.com , https://github.com/App-vNext/Polly/wiki/Unit-testing-with-Polly. Thoughts/questions about unit-testing? Parabolic, suborbital and ballistic trajectories all follow elliptic paths. How my code behaves when the policy throws an exception, such as TimeoutRejectionException, BulkheadRejectedException or BrokenCircuitException. 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. Therefore, the call to Random.Next() has to be locked. 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. Lets extend it a bit. It will authenticate first (the authentication service itself will also use Polly) and try to get products. 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. It reduces pressure on the server, which decreases the chances of running into transient errors. Ill show the client and service (stubbed to return the error response) code below and the results of running it. This is (almost) the shortest xUnit test I could write that HttpClientFactory does correctly configure and use a policy. I guess I should be able to create an exact test but for demonstration purposes this will serve its purpose. Please note the new name SetWaitAndRetryPolicy2. One of those classes is System.Net.HttpClient class. Use the one that makes the most sense in your scenario. HTTP Retry with Polly | Carl Paton | There are no silly questions Adding Polly retry policy to a mocked HttpClient? C# "internal" access modifier when doing unit testing. 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. 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?) You can then use these values to sort and group tests in Test Explorer. What's the function to find a city nearest to a given latitude? To do this, it can be helpful to mock your Polly policy to return particular results or throw particular outcomes on execution. To make use of this injected service, we need to inject it in the class controller. The button and/or link above will take To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Implementing the Circuit Breaker pattern | Microsoft Learn Why did US v. Assange skip the court of appeal? 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. Lets try and implement the same scenario in a more clean and maintainable way by using Polly! Discover .NET - Polly Visual Studio 2017 and later (Professional and Enterprise), Visual Studio 2017 and later (all editions). Please note the new name RetryPolicyTests2 . I updated my existing integration test method to below, but the retry policy is not activated. Which language's style guidelines should be used when writing code that is supposed to be called from another language? At the end, Ill show a full example of retrying HttpClient requests with Polly. See these example links: 1; 2; 3; 4. Using an Ohm Meter to test for bonding of a subpanel. Refactor to inject the Policy into the method/class using it (whether by constructor/property/method-parameter injection - doesn't matter). 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. Use DI to provide policies to consuming classes; tests can then stub out Polly by injecting NoOpPolicy in place of real policies. 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. That could be with a full DI container, or just simple constructor injection or property injection, per preference. Applies to: Visual Studio Visual Studio for Mac Visual Studio Code. Not the answer you're looking for? An application can combine these two patterns. Build Resilient HTTP Clients in C# on .NET 6 With Polly 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. The basic configuration is similar for both the Microsoft and Google Test frameworks. retryAttempt => TimeSpan.FromSeconds(Math.Pow(retrySleepDuration, retryAttempt)), InlineData(1, HttpStatusCode.RequestTimeout), InlineData(0, HttpStatusCode.InternalServerError), GetRetryPolicy_Retries_Transient_And_NotFound_Http_Errors. The Polly .NET library helps simplify retries by abstracting away the retry logic, allowing you to focus on your own code. Install nuget Microsoft.Extensions.Http.Polly. A boy can regenerate, so demons eat him for years. If you write your own integration tests around policies in your project, note the possibility to manipulate Polly's abstracted SystemClock. I think most of us, at some point in time, we saw code like this, trying to implement some kind of retry logic. After the final attempt, it stopped retrying and let the exception bubble up. http://www.introtorx.com/Content/v1.0.10621.0/16_TestingRx.html#TestScheduler for more information. Unit testing retry policies with timeout intervals #156 - Github I am using polly to handle retry (see below code). To produce a test result, use the static methods in the Assert class to test actual results against expected results. For more information, see To link the tests to the object or library files. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? For more information, see How to: Use CTest in Visual Studio. Thanks for contributing an answer to Stack Overflow! We use it so often to make web requests. GitHub blocks most GitHub Wikis from search engines. Unit testing with Polly - App-vNext/Polly GitHub Wiki 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. When developing an application with Polly you will also probably want to write some unit tests. Lets say I have a micro service with an API endpoint to retrieve products: Could everything just be as simple as that. 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. So, lets say hi to the circuit breaker. Adding Polly retry policy to a mocked HttpClient? For Google Test documentation, see Google Test primer. To enable access to the functions in the project under test, add a reference to the project in your test project. Refactor to inject the Policy into the method/class using it (whether by constructor/property/method-parameter injection - doesn't matter). How can I unit test polly retry? The circuit breaker keeps track of the number of exceptions. The Polly policy is configured within the test. Does anyone know who is caching the response, and how do I disable it? Boost.Test requires that you manually create a test project. Perhaps you have code modules for which you already had unit tests, including success and failure cases. How can one simulate all the scenarios at a time to verify the behavior of all policies? This angle on testing aims to check you've configured policies to match your desired resilience behaviour. 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. The class below implements this calculation: (1 second * 2^attemptCount-1) + random jitter between 10-200ms. You should only retry if the attempt has a chance of succeeding. Example: Thanks for contributing an answer to Stack Overflow! If somebody changes the configuration, the test provides regression value by failing. The following illustration shows a test project whose tests have not yet run. I want to unit test a polly retry logic. There are multiple endpoints, all authenticated with OAuth. Why did DOS-based Windows require HIMEM.SYS to boot? c# - Polly retry unit test - Stack Overflow For more information, see How to: Use Boost.Test in Visual Studio. Writing unit-tests to verify that Polly works can be a very valuable way to explore and understand what Polly does. I do like writing unit tests but especially when programming difficult scenarios with APIs and policies. Some time ago I wrote an article which explains how to Increase service resilience using Polly and retry pattern in ASP.NET Core. 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. Theres only one instance of Random, and there could be multiple threads making requests concurrently. It was just a trigger for me to write about Polly. Whenever youre dealing with code that can run into transient errors, its a good idea to implement retries. in order to trigger Polly's fault and resilience policies such as WaitAndRetry. CTest support is included with the C++ CMake tools component, which is part of the Desktop development with C++ workload. It will break when the configured number of exceptions have been thrown. Some features such as Live Unit Testing, Coded UI Tests and IntelliTest aren't supported for C++. 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. Please view the original page on GitHub.com and not this indexable TEST_CLASS and TEST_METHOD are part of the Microsoft Native Test Framework. Queston 1: Am I missing something? A TEST_METHOD returns void. Lets work on another revision of the code to add extra retries for these scenarios: I am going to stop right here. 0 comments Enigma94 commented on Apr 28, 2020 What I am trying to do: Throw SqlException in ExecuteAsync 2 times 3rd time return true What actually happens: Throws SqlException in ExecuteAsync 1 time Unit test fails According to my understanding in your provided sample you are making asserting only against the result. Define and run unit tests inside one or more test projects. Do all the tests need adjusting? You signed in with another tab or window. Edit and build your test project or solution. I want to find out how Polly retry polly configured via Startup.ConfigureServices() can be tested. Was Aristarchus the first to propose heliocentrism? How to verify that method was NOT called in Moq? How do I stop the Flickering on Mode 13h? I posted the same question on StackOverflow a few weeks ago without any answer. If it fails with a different exception or status code, it propagates the exception to the caller. ErrorProneCode.cs is the unreliable class that I will mock and pass mocked policies into. 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). Imagine this: I want a retry on the authentication api but only when I receive a RequestTimeout (Http status code 408). In this section, Ill only try to handle one: the Too Many Requests error response (429). Implement the retry delay calculation that makes the most sense in your situation. Let's see how our unit test for the controller method from above would look like. Several third-party adapters are available on the Visual Studio Marketplace. Test Polly retry polly configured via Startup.ConfigureServices() with ASP.NET Core API. However, I still have problem getting the named HttpClient, and other questions. using xunit and moq. 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. To make sure all calls to the APIs will have a high success rate I had to implement retry mechanisms for different scenarios. rev2023.5.1.43404. What are the advantages of running a power tool on 240 V vs 120 V? I actually just found what I was looking for in Polly itself! 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. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, C# Kafka: How to Create a NetworkException Error, Unit testing internal methods in VS2017 .NET Standard library, Using Polly to retry on different Urls after failing retries. For instance, you may want to test how your code reacts if, despite resilience strategies, the execution eventually fails. tar command with and without --absolute-names option. Can be useful as a specification for, and regression check on, the faults you intend to handle. You would use Mountebank or HttpClientInterception to stub the outbound call from HttpClientService to return something the policy handles eg HttpStatusCode.InternalServerError, in order to trigger the Polly retry policy. I don't want to wait more than one minute in my tests. 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. Test Polly retry polly configured via Startup - Github How to add clean Retrying in .NET Core using Polly - YouTube A common need is to test the logic of your system-under-test as if Polly were not part of the mix. Don't include object files that have a main function or another standard entry point such as wmain, WinMain, or DllMain. Published with Wowchemy the free, open source website builder that empowers creators. The code is simple, it hardly needs further explanation. privacy statement. Did the drapes in old theatres actually say "ASBESTOS" on them?
