xRetry

Retry flickering test cases for xUnit.

When to use this

This is intended for use on flickering tests, where the reason for failure is an external dependency and the failure is transient, e.g:

• HTTP request over the network
• Database call that could deadlock, timeout etc...

Whenever a test includes real-world infrastructure, particularly when communicated with via the internet, there is a risk of the test randomly failing so we want to try and run it again. This is the intended use case of the library.

If you have a test that covers some flaky code, where sporadic failures are caused by a bug, this library should not be used to cover it up!

Usage: xUnit

Add the xRetry nuget package to your project.

Facts

Above any Fact test case that should be retried, replace the Fact attribute, with RetryFact, e.g:

private static int defaultNumCalls = 0;

[RetryFact]
public void Default_Reaches3()
{
    defaultNumCalls++;

    Assert.Equal(3, defaultNumCalls);
}

This will attempt to run the test until it passes, up to 3 times by default. You can optionally specify a number of times to attempt to run the test as an argument, e.g. [RetryFact(5)].

You can also optionally specify a delay between each retry (in milliseconds) as a second parameter, e.g. [RetryFact(5, 100)] will run your test up to 5 times, waiting 100ms between each attempt.

Theories

If you have used the library for retrying Fact tests, using it to retry a Theory should be very intuitive.
Above any Theory test case that should be retried, replace the Theory attribute with RetryTheory, e.g:

// testId => numCalls
private static readonly Dictionary<int, int> defaultNumCalls = new Dictionary<int, int>()
{
    { 0, 0 },
    { 1, 0 }
};

[RetryTheory]
[InlineData(0)]
[InlineData(1)]
public void Default_Reaches3(int id)
{
    defaultNumCalls[id]++;

    Assert.Equal(3, defaultNumCalls[id]);
}

The same optional arguments (max attempts and delay between each retry) are supported as for facts, and can be used in the same way.

Skipping tests at Runtime

In addition to retries, RetryFact and RetryTheory both support dynamically skipping tests at runtime. To make a test skip just use within your test code. It also supports custom exception types so you can skip a test if a type of exception gets thrown. You do this by specifying the exception type to the attribute above your test, e.g.