DLR/dynamic support

[artkpv]

Hi,
Is there a way to make FluentAssertions work with dynamic/DLR? Consider the following code:

dynamic expando = new ExpandoObject();
expando.someVar = "string";
expando.someVar.Should().Be("string");

which throws Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: "'string' does not contain a definition for 'Should'"

Thanks!

[dennisdoomen]

Not until C# supports calling extension methods from dynamic objects...

[adamvoss]

Usually dynamic users can still utilize Extension Methods by calling them as static methods. Can anything reasonably be changed internally in FA to support this?

As is a StackOverflowException is thrown by the following example. I only assume that it managed to get caught in some sort of infinite recursion between overloaded methods.

string d = "hi";
AssertionExtensions.Should(d).Be("yo");

Given a number of the recent .NET targets do not support dynamic I am not sure it is oft used enough that FA needs cater to it. However, I believe it would at least be possible to at least prevent stack overflow by adding a Should(dynamic) method on platforms that support it.

Since NUnit's Assert.That constraint-based assertions do depend on the objects' types you might find those more suitable. Alternatively, you could of course cast your dynamic object to be able to us FA's assertions.

[dennisdoomen]

@vossad01 But what should Should(dynamic) do?

[JowenMei]

Can't you use the equality operator, like in Assert.AreEqual()?
I'm also looking for a fluent alternative for:
Assert.AreEqual(controller.ViewBag.HelpUrl, "helpUrl value from settings");

[mpodonyi]

Is it not possible to use .As<T>() or .BeOfType<>() method to cast the dynamic value to a concrete one.
e.g:

dynamic set = GetDynamic();
set.As<int>().Should().Be(6);

Looks better than:

dynamic set = GetDynamic();
((int)set).Should().Be(6);

[artkpv]

@mpodonyi That .As<T>() does not work. Throws Microsoft.CSharp.RuntimeBinder.RuntimeBinderException. As @dennisdoomen wrote DLR does not support extension methods so far. Here is interesting discussion. In short it can't search the method at runtime to match the object.

[TroySijuwade]

@artkpv , @JowenMei I note this is over 2 years late ;) ... and for the benefit of those still trying to figure out how to do this, I was able to do this using FluentAssertions:

((string) result.ViewBag.HelpUrl).ShouldBeEquivalentTo("helpUrl value from settings");

[dennisdoomen]

The situation will be a bit better with 5.0 because the object being compared with will be what is used to traverse the object graph instead of the SUT.

[WhatFreshHellIsThis]

Has anything now changed with 5.0? (I need to test dynamic objects with a REST api)
I want to check if a dynamic object has a property or not for starters.

[dennisdoomen]

Unless there's a way to define a Should() extension method that acts on dynamic, no

[lycandroid]

I am using cast to object as a workaround, but where I am specifically wanting to test the type of a dynamic e.g.

// field.value is dynamic
field.value = "xyz";
((object)field.value).Should().BeOfType(typeof(string));

FWIW the same cast would work for the OP

 ((object)expando.someVar).Should().Be("string");