Add Assert.IsType<T>(object obj)

[spottedmahn]

Description

xUnit has a nice Assert method: public static T IsType<T>(object @object) that is lacking from MS Test.

MS Test has an "old" method: Assert.IsInstanceOfType(object, typeof(object)). This feels very .Net 1.1 w/o generics.

xUnit Advantages

1. The xUnit method uses generics making it cleaner IMHO
2. The xUnit method returns the object (allows for clean one-liner)

Code Comparison

var badRequestResult = Assert.IsType<BadRequestObjectResult>(result);

//do stuff with badRequestResult
var blah = badRequestResult.Value;
...

vs

var badRequestResult = result as BadRequestObjectResult;
Assert.IsInstanceOfType(badRequestResult, typeof(BadRequestObjectResult));

//do stuff with badRequestResult
var blah = badRequestResult.Value;
...

Open to Adding?

What to do you think about extending the Assert API?

---

Reference: SO Post: xUnit.net IsType Equivalent in MS Test That Returns Type

AB#1614478

[AbhitejJohn]

@spottedmahn : Would this help? It does have the specific example you referred to. I agree that this would be nice addition in-box though.

[spottedmahn]

Hi @AbhitejJohn - that is close!

It should return the strongly typed object if it is that type IMO.

public static class SampleAssertExtensions
{
	public static T IsOfType<T>(this Assert assert, object obj)
	{
		if(obj is T result)
		{
			return result;
		}
		throw new AssertFailedException("Type does not match");
	}
}

[spottedmahn]

I like this btw Assert.That.IsNotNull(animal).And.IsOfType<Cat>(animal)! 👍⚡

[AbhitejJohn]

@spottedmahn : yeah, I like the chaining a lot too. Makes things easier to express and its readable. Agree on the strong name typing. You might want to add that into a custom extension in your code base or possibly also add that out as a library. I've created one for asserts over exception handling based off of this but I can imagine others extending this out for type checking/comparison too.

[spottedmahn]

Hey @AbhitejJohn - that's brilliant 💲... create an extension library that can move much faster than the full library 🌉. Like VS Power Tools!

I'll put in PR for public static T IsOfType<T>(this Assert assert, object obj)!

[AbhitejJohn]

I actually just put that out, so I can go crazy with this extension point and also see if it works for consumers. From the download count, it does look useful. The core framework would still want to update itself with a few of these APIs that everyone would need just so there isn't an extra step to find and pull in another package but that's a choice for the framework now.

[spottedmahn]

I think it is great, put something out there. If it works and gains traction, put it in the core lib!

[pascalpfeil]

+1 on this, this would clean up so many of my tests.