Add test for error handling when argument is not an array

Author: alexandru-pocovnicu

Sprint-2/implement/lookup.test.js

@@ -10,6 +10,11 @@ test("creates a country currency code lookup for multiple codes", () => {
   ).toEqual({ US: "USD", CA: "CAD", RO: "RON" });
 });
 
+test("throw error if the argument is not an object", () => {
+  expect(() => createLookup("notAnObject")).toThrow(
+    "Argument must be an array"
+  );
+});
 /*
 
 Create a lookup object of key value pairs from an array of code pairs