A Reqnroll plugin to automatically retry failed steps

Why retry?

When your System Under Test (SUT) runs asynchronously, it needs time to reach the correct state. During this time your Then steps should not fail, execution of it needs to:

1. Complete when it runs successfully. This avoids unnecessary delays.
2. Retry when it throws during the allowable time.
3. Stop and throw last exception when the maximum time is reached.

How to use it

Register a IRetryStepPluginConfiguration in the scenario container. This object is responsible to decide which step-definitions are eligible for retry. Additionally, register a IAsyncRetryer. This object is responsible for doing the retry logic.

For example:

[BeforeScenario]
public static void BeforeScenario(IObjectContainer c)
{
    c.RegisterInstanceAs<IRetryStepPluginConfiguration>(new RetryThen());
    c.RegisterInstanceAs<IAsyncRetryer>(new PollyRetryer());
}

//This test project wants all `Then` steps to be retried.
public class RetryThen : IRetryStepPluginConfiguration
{
    public bool RetryEnabledFor(BindingMatch match) 
    => match.StepBinding.StepDefinitionType == StepDefinitionType.Then;
}

[Then("this step definition will be retried in case of transient failures")]
public void DoCheck() => MySystem.State.Should().BeOK();

How the plugin is implemented

The plugin registers a custom ITestExecutionEngine. This custom engine derives from the default Reqnroll TestExecutionEngine but overrides the ExecuteStepMatchAsync method to:

1. Retrieve the IRetryStepPluginConfiguration from the ScenarioContainer and ask if the current BindingMatch should be retried.
2. If retry is needed, it retrieves an IAsyncRetryer from the ScenarioContainer to perform the retry logic on the invocation of the binding like this

await Retryer.RetryAsync(async () => await _bindingInvoker.InvokeBindingAsync(match.StepBinding, _contextManager, arguments, _testTracer, durationHolder));