diff --git a/test/cryogen_core/classpath_able_io_test.clj b/test/cryogen_core/classpath_able_io_test.clj
index 019df5d..3e51390 100644
--- a/test/cryogen_core/classpath_able_io_test.clj
+++ b/test/cryogen_core/classpath_able_io_test.clj
@@ -16,6 +16,9 @@
        (.isDirectory (io/file path))))
 
 (deftest test-file-from-cp-or-filesystem
+  (is (thrown? IllegalArgumentException
+                     (sut/file-from-cp-or-filesystem
+                      "./" "Not_Existing")))
   (is
    (.exists (sut/file-from-cp-or-filesystem 
              "./test-resources/" "templates/themes/bootstrap4-test/js")))