InstanceOfTypeConstraint - jnm2/nunit-docs-wiki GitHub Wiki
InstanceOfTypeConstraint tests that an object is of the type supplied or a derived type.
InstanceOfTypeConstraint(Type)Is.InstanceOf(Type)
Is.InstanceOf<T>()Assert.That("Hello", Is.InstanceOf(typeof(string)));
Assert.That(5, Is.Not.InstanceOf(typeof(string)));
Assert.That(5, Is.Not.InstanceOf<string>());