msvc is_copy_assignable always true?

#include <type_traits>

class Test
{
public:
    Test(const Test &) = delete;
    Test &operator=(const Test &) = delete;
};

void fn(Test &a, const Test &b) { a = b; }

static_assert(!std::is_copy_assignable<Test>::value, "Test shouldn't be assignable");

Compiling this under MSVC 2013 Update 3 unexpectedly fails the static_assert, and the function fn fails to compile (as expected.) This is contradictory, right?

Am I misusing is_copy_assignable? Is there another way to test for this condition?