:). Can it still be improved? The text was updated successfully, but these errors were encountered: Hi @jiimaho A good strategy for this could be Dependency Injection: Hi @reisenberger and thanks for your quick reply. This property was added in .NET 5 (finally!). 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. using AutoFixture . 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. I will answer the question at three different levels, and you can choose what suits best. When developing an application with Polly you will also probably want to write some unit tests. sleepDurationProvider: retryDelayCalculator.Calculate, "https://localhost:12345/weatherforecast", Executing logic between retries with the onRetry parameter, Full example Retrying HttpClient requests with Polly, WeatherClient Retries HttpClient requests with Polly, WeatherService A service stub that intentionally returns errors, Retry delay calculation: Exponential backoff with jitter, C# Check if a string contains any substring from a list. I guess I should be able to create an exact test but for demonstration purposes this will serve its purpose. Check out my Pluralsight course on it. The button and/or link above will take Ill show the client and service (stubbed to return the error response) code below and the results of running it. 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. What my code should do if there was no policy in place. 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. Making statements based on opinion; back them up with references or personal experience. Lets say I created a micro service to create orders. When all retry attempts fail, it fails. You can then use these values to sort and group tests in Test Explorer. 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. Boolean algebra of the lattice of subspaces of a vector space? I think most of us, at some point in time, we saw code like this, trying to implement some kind of retry logic. C# - Retry Pattern with Polly - Code4Noobz Setting upIHttpClientFactory is quite easy in ASP.NET Core container setup in Startup.cs. 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. Install nuget Microsoft.Extensions.Http.Polly. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. You can use the onRetry method to try to fix the problem before the next retry attempt. When you retry without a delay, it means youll be changing something that should fix the problem so that the retries succeed. 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. Unit testing with Polly - App-vNext/Polly GitHub Wiki Want to learn more about Polly? Find centralized, trusted content and collaborate around the technologies you use most. Using Polly for retrial policies with Autofac - WebLog The test simply proves that HttpClientFactory does configure the HttpClient to use the policy. Use DI to provide policies to consuming classes; tests can then stub out Polly by injecting NoOpPolicy in place of real policies. 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. This means when the retry conditions are met, it retries the request. To add a new test project to an existing solution. The 3rd parameter of onRetry is an int which represents retryAttempt, this can be added to logs. Refactor to inject the Policy into the method/class using it (whether by constructor/property/method-parameter injection - doesn't matter). In the following example, assume MyClass has a constructor that takes a std::string. For more information, see How to: Use Google Test in Visual Studio. C# Quicktip: In Xunit how to skip a unit test from being run The .cpp file in your test project has a stub class and method defined for you. Please refer to my updated comments at the bottom of OP. .NET Core: Use HttpClientFactory and Polly to build rock solid services Heres a simple example of using Polly to do retries with a delay. Has the Melford Hall manuscript poem "Whoso terms love a fire" been attributed to any poetDonne, Roe, or other? This is (almost) the shortest xUnit test I could write that HttpClientFactory does correctly configure and use a policy. Guess not! c# - Testing Polly retry policy with moq - Stack Overflow Why are players required to record the moves in World Championship Classical games? I Honestly love this approach, thanks for the article, this was really helpful, i was able to get a simple retry working using this. Edit and build your test project or solution. With Polly it is possible to create complex and advanced scenarios for error handling with just a few lines of code. Where a test would usually incur a delay (for example, waiting the time for a circuit-breaker to transition from open to half-open state), manipulating the abstracted clock can avoid real-time delays. github.com/justeat/httpclient-interception, How a top-ranked engineering school reimagined CS curriculum (Ep. On the Test menu, choose Windows > Test Explorer. In the next case I verify that the application has correctly used the retry policy method. I use a seeded random number generator that produces an known sequence to return values from the ErrorProneCode class. Unit testing retry policies with timeout intervals, http://www.introtorx.com/Content/v1.0.10621.0/16_TestingRx.html#TestScheduler. No problem, glad it could help. For more information on unit testing, see Unit test basics. For . 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. This page also exists in a longer version with worked examples, How to approach unit-testing code wrapped in Polly policies depends what you are aiming to test. For more information about using Test Explorer, see Run unit tests with Test Explorer. How a simple API call can get way too complex 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? It will retry up to 3 times. To do this, it can be helpful to mock your Polly policy to return particular results or throw particular outcomes on execution. Finally, I want to verify that my code will work if no Polly policy is in use. 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). @reisenberger I think it's good to let consumers of the Polly API be able to provide a time-provider. C# Polly WaitAndRetry policy for function retry, Unit test Polly - Check whether the retry policy is triggered on timeout / error. To provide stub responses to that downstream call (not shown in the code posted in the question, I don't know what it is), you could use either: HttpClientInterception provides a good sample app which demonstrates how to set up HttpClientInterception to provide stub responses to outbound calls which your app makes. Therefore, the call to Random.Next() has to be locked. If somebody changes the configuration, the test provides regression value by failing. How can I unit test polly retry? Here are the scenarios I test for - How my code behaves when the policy throws an exception, such as TimeoutRejectionException, BulkheadRejectedException or BrokenCircuitException. Did the drapes in old theatres actually say "ASBESTOS" on them? When the configured delay time has been passed it will reset the circuit and start all over. Do all the tests need adjusting? The simplest way to check how many times code was executed is by using a mock. Unit Testing retry policy with SqlExceptions #768 - Github Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. as GitHub blocks most GitHub Wikis from search engines. So, this code does not test any part of the original code. When sending concurrent requests with HttpClient, its a good idea to use the same instance repeatedly. However, there are a lot of classes that re commonly used which are not refactored in .NET Core. That could be with a full DI container, or just simple constructor injection or property injection, per preference. To make use of this injected service, we need to inject it in the class controller. If that code expectation is not all wired up properly inside the app, it could be a cause of test failure. Type #include ", and then IntelliSense activates to help you choose. appsettings.json). In the DI container set the handler to be applied to the injected http client, this will be avalible to the constructor of FooService. There are no ads in this search engine enabler service. you directly to GitHub. For Google Test documentation, see Google Test primer. There is no need for any WebApplicationFactory, IHost, IHostedService or anything from ASP.NET. The WeatherClient contains this single HttpClient instance. It will retry for a number of time when receiving any exception. You can download the Google Test adapter and Boost.Test Adapter extensions on the Visual Studio Marketplace. Where can I find a clear diagram of the SPECK algorithm? Create the projects in the same solution as the code you want to test. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. In addition, it creates and contains the AsyncRetryPolicy (Note: You could pass it in instead). I figured it out. Adding Polly retry policy to a mocked HttpClient? 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. Test Polly retry polly configured via Startup - Github But the next problem arises: the API is going to be protected with OAuth so we have to get an access token from another endpoint and provide a bearer token to be able to retrieve products. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. When theres an error, it retries, and then succeeds 3. After all the tests run, the window shows the tests that passed and the ones that failed. I also wasnt sure on the value of using async when its just a log, so I switched it out. 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. 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). Some transient errors can be fixed by delaying for a short time. ErrorProneCode.cs is the unreliable class that I will mock and pass mocked policies into. There are many overloads that you can choose to implement. When developing an application with Polly you will also probably want to write some unit tests. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? It is documented here: Microsoft.VisualStudio.TestTools.CppUnitTestFramework API reference. I like the way you explain things, tell why, and offer alternatives. The only difference is I made it randomly return the 429 error status code.
