Cannot read dynamic properties with FluentAssertions

Question

I am using XUnit and fluentassertions in c sharp for my unit tests. Below is where I get a dynamic type, convert a dynamic object to that dynamic type and try to do an assertion:

        var dynamicType = Type.GetType(...);

        dynamic? myObject = JsonSerializer.Deserialize(myJSONData, dynamicType);

        myObject!.Products!.Should().NotBeNull();

If I debug it, myObject does have the required properties and values, however c sharp and fluentassertion throw this error:

  Microsoft.CSharp.RuntimeBinder.RuntimeBinderException : 'xxxxx.Products' does not contain a definition for 'Should'

Is it possible to do the comparison or did I miss out anything?

score 4 · Accepted Answer · answered Mar 30 '22 at 11:22

It's a limitation in .NET. It does not support extension methods for dynamic objects.

A workaround is to cast myObject into an object, such that the appropriate overload of Should can be determined at compile time.

Some related issues:

score 0 · Answer 2 · answered Mar 30 '22 at 14:14

0

This is a simple way to do it, just add (object) cast in front of the assert if your object is dynamic.

(object) myObject!.Products!.Should().NotBeNull();

You need to import System.Object.

answered Mar 30 '22 at 14:14

avdeveloper

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Cannot read dynamic properties with FluentAssertions

2 Answers2