How to assert that collection is IReadOnlyCollection using NUnit

Question

I have a method in SomeClass , which return IReadOnlyCollection . Something like that:

public calss SomeClass
{
   private readonly List<Part> _parts;

   ...

   public IReadOnlyCollection<Part> GetAllParts =>
            this._parts;
}

In my Unit tests I want to assert that returned collection ( expectedCollection ) is IReadOnlyCollection. I have tried with reflection:

[Test]
public void TestWariorsShoudReturnReadOnlyCollectionOfWariors()
{
    var expectedCollection = MyPartsLib.GetAllParts;

    Type type = expectedCollection.GetType();
    string acctualtypeName = type.Name;
    string expectedTypeName = "IReadOnlyCollection";
    Assert.AreEqual(expectedTypeName,acctualtypeName);
}

But acctualtypeName after executing is List`1 . How can I assert that expectedCollection is IReadOnlyCollection ?

Thanks for you help.

Answer 1

You can use is operator for type checking

[Test]
public void TestWariorsShoudReturnReadOnlyCollectionOfWariors()
{
    var expectedCollection = MyPartsLib.GetAllParts;
    Assert.True(expectedCollection is IReadOnlyCollection<Part>);
}

Answer 2

You can also use

...
Assert.IsInstanceOfType(expectedCollection, typeof(IReadOnlyCollection<Part>));
...

which results in a clear assertion message pointing out that the wrong type was retrieved.