Update querystring.test.js to clarify spec

Author: cjyuan

Sprint-2/implement/querystring.test.js

@@ -1,12 +1,48 @@
 // In the prep, we implemented a function to parse query strings.
 // Unfortunately, it contains several bugs!
-// Below is one test case for an edge case the implementation doesn't handle well.
-// Fix the implementation for this test, and try to think of as many other edge cases as possible - write tests and fix those too.
+// Below are some test cases the implementation doesn't handle well.
+// Fix the implementation for these tests, and try to think of as many other edge cases as possible - write tests and fix those too.
 
 const parseQueryString = require("./querystring.js")
 
-test("parses querystring values containing =", () => {
-  expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
+test("should parse values containing '='", () => {
+  expect(parseQueryString("equation=a=b-2")).toEqual({
+    equation: "a=b-2",
+  });
+});
+
+test("should ignore empty key-value pairs", () => {
+  expect(parseQueryString("key1=value1&&key2=value2&")).toEqual({
+    key1: "value1",
+    key2: "value2",
+  });
+});
+
+test("should accept empty string as key or as value", () => {
+  expect(parseQueryString("=value")).toEqual({ "": "value" });
+  expect(parseQueryString("key")).toEqual({ key: "" });
+  expect(parseQueryString("key=")).toEqual({ key: "" });
+  expect(parseQueryString("=")).toEqual({ "": "" });
+});
+
+test("should decode percent-encoded characters", () => {
+  expect(parseQueryString("%24half=1%2F2")).toEqual({
+    $half: "1/2",
+  });
+});
+
+test("should replace '+' by ' '", () => {
+  expect(parseQueryString("full+name=John+Doe")).toEqual({
+    "full name": "John Doe",
+  });
+});
+
+// Stretch exercise: Handling query strings that contain identical keys
+
+// Delete this test if you are not working on this optional case
+test("should store values of a key in an array when the key has 2 or more values", () => {
+  expect(parseQueryString("key=value1&key=value2&key=value3&foo=bar")).toEqual({
+    key: ["value1", "value2", "value3"],
+    foo: "bar",
   });
 });