fix test copy paste error. Add test case for when query string is "&" or "&&"

Author: RaihanSharif

Sprint-2/implement/querystring.test.js

@@ -12,7 +12,7 @@ test("empty query string returns {}", () => {
 });
 
 // null or undefined
-test("empty query string returns {}", () => {
+test("null or undefined input returns {}", () => {
   expect(parseQueryString(null)).toEqual({});
   expect(parseQueryString(undefined)).toEqual({});
   expect(parseQueryString()).toEqual({});
@@ -81,3 +81,8 @@ test("trims whitespace from keys and values", () => {
     age: "30",
   });
 });
+
+test("string with only delimiters returns {}", () => {
+  expect(parseQueryString("&")).toEqual({});
+  expect(parseQueryString("&&")).toEqual({});
+});