diff --git a/test.lua b/test.lua
index 2731fd9..65eee6e 100644
--- a/test.lua
+++ b/test.lua
@@ -159,6 +159,9 @@ test("Testing is_instance", function()
     fv = FooVec(1,2)
     assert(FooVec:is_instance(fv))
     assert(not FooVec:is_instance(v))
+    assert(not FooVec:is_instance("asdf"))
+    assert(not FooVec:is_instance({}))
+    assert(not FooVec:is_instance(5))
 end)
 
 test("Testing spoofing", function()