FluentAssertions ShouldNotThrow is not recognised for an async method/Func

Question

I am trying to check an async method throws concrete exception.

For that I am using MSTEST and FluentAssertions 2.0.1.

I have checked this Discussion on Codeplex and to see how it works with async-exception methods this another one link about FluentAssertions async tests:

After a while trying to work with my 'production' code I have switched off to the Fluentassertions fake aync class and my resulting code is like this (put this code inside a [TestClass]:

[TestMethod]
public void TestThrowFromAsyncMethod()
{
    var asyncObject = new AsyncClass();
    Action action = () =>
    {
        Func<Task> asyncFunction = async () =>
        {
            await asyncObject.ThrowAsync<ArgumentException>();
        };
        asyncFunction.ShouldNotThrow();
    };
}


internal class AsyncClass
{
    public async Task ThrowAsync<TException>()
        where TException : Exception, new()
    {
        await Task.Factory.StartNew(() =>
        {
            throw new TException();
        });
    }

    public async Task SucceedAsync()
    {
        await Task.FromResult(0);
    }
}

The problem is that ShouldNotThrow is not valid:

ShouldNotThrow method is not recognised by the code. If I try to compile, it gives me this error: 'System.Func' does not contain a definition for 'ShouldNotThrow' and the best extension method overload 'FluentAssertions.AssertionExtensions.ShouldNotThrow(System.Action, string, params object[])' has some invalid arguments

Thanks.

---

SOLUTION

2.0.1 FA version doesn't support this ShouldNotThrow functionality and it will be included in the next reléase 2.1 (near next week).

Note: ShouldThrow is already supported in 2.0.1 versión.

Answer 1

You don't need the encompassing Action. That is only used in the unit tests to verify that the API is throwing the right exception. This should be sufficient:

[TestMethod]
public void TestThrowFromAsyncMethod()
{
    Func<Task> asyncFunction = async () =>
    {
        await asyncObject.ThrowAsync<ArgumentException>();
    };

    asyncFunction.ShouldNotThrow();
}

Unfortunately the ShoudlNotThrow() on a Func is missing from .NET 4.5. I've fixed this in release 2.1 (currently dogfooding).