public void TestInterfaceProxyMethodVariance()
{
Duck duck = new Duck();
IInterface proxy = DuckTyping.Cast <IInterface>(duck);
string stringValue = "String value.";
int intValue = 5;
Assert.AreEqual(stringValue, proxy.ContravariantMethod(stringValue), "Contravariant method returned wrong value.");
Assert.IsNull(proxy.ContravariantMethod(null), "Passing and returning a null value to and from a contravariant method failed.");
try
{
proxy.ContravariantMethod(new object[0]);
Assert.Fail("Passing a non-string object through a contravariant method that takes a string parameter should have thrown an InvalidCastException.");
}
catch (InvalidCastException)
{ }
try
{
proxy.ContravariantValueMethod(7);
Assert.Fail("Passing a non-DateTime object through a contravariant method that takes a DateTime parameter should have thrown an InvalidCastException.");
}
catch (InvalidCastException)
{ }
try
{
proxy.ContravariantValueMethod(null);
Assert.Fail("Passing null through a contravariant method that takes a value type parameter should have thrown a NullReferenceException.");
}
catch (NullReferenceException)
{ }
Assert.AreEqual("Method", proxy.ContravariantEnumMethod("Method"), "Contravariant method returned wrong enum value.");
try
{
proxy.ContravariantEnumMethod(null);
Assert.Fail("Passing null through a contravariant method that taks an enum parameter should have thrown a NullReferenceException.");
}
catch (NullReferenceException)
{ }
Assert.AreEqual(stringValue, proxy.CovariantMethod(stringValue), "Covariant method returned wrong value.");
Assert.IsNull(null, proxy.CovariantMethod(null), "Passing and returning a null value to and from a covariant method failed.");
Assert.AreEqual(intValue, proxy.CovariantValueMethod(intValue), "Covariant method returned wrong int value.");
Assert.AreEqual(AttributeTargets.Class, proxy.CovariantEnumMethod(AttributeTargets.Class), "Covariant method returned wrong enum value.");
// Note: This next line is primarily to check whether the system handles a recursive cast properly. If it doesn't,
// a StackOverflowException will be thrown.
Assert.IsTrue(proxy.Equals(proxy.VariantByRecursiveCastMethod(duck)), "Variant by recursive cast method returned wrong value.");
Assert.AreEqual(duck, proxy.VariantByUncastMethod(proxy), "Variant by uncast method returned wrong value.");
}