diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..fde180d6d 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -12,4 +12,4 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address["houseNumber"]}`);
diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..7ba8f4c75 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -11,6 +11,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..a413b3332 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -12,4 +12,4 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join("\n")}`);
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..cf2d0757a 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,5 @@
-function contains() {}
+function contains(obj, property_name) {
+  return property_name in obj;
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..aa1f35ebe 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,16 +20,28 @@ as the object doesn't contains a key of 'c'
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("contains on empty object returns false", () => {
+  expect(contains({}, "a")).toBe(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("returns true when object contains an existing property", () => {
+  expect(contains({ a: 1, b: 2 }, "a")).toBe(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("returns false when object does not contain the property", () => {
+  expect(contains({ a: 1, b: 2 }, "c")).toBe(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("returns false or throws an error when passed invalid parameters like an array", () => {
+  expect(() => contains([], "a")).not.toThrow();
+  expect(contains([], "a")).toBe(false);
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..4373213ac 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,11 @@
-function createLookup() {
+function createLookup(country_currency_pairs) {
   // implementation here
+      const lookup = {};
+      for (const [country, currency] of country_currency_pairs) {
+        lookup[country] = currency;
+    }
+
+    return lookup;
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..beb33b5b3 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,7 +1,5 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
-
 /*
 
 Create a lookup object of key value pairs from an array of code pairs
@@ -33,3 +31,37 @@ It should return:
    'CA': 'CAD'
  }
 */
+
+test("creates a country currency code lookup for multiple codes", () => {
+  const countryCurrencyPairs = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  const result = createLookup(countryCurrencyPairs);
+
+  expect(result).toEqual({
+    US: "USD",
+    CA: "CAD",
+  });
+});
+
+test("creates a country currency code lookup for a single code", () => {
+  const countryCurrencyPairs = [
+    ["GB", "GBP"],
+  ];
+
+  const result = createLookup(countryCurrencyPairs);
+
+  expect(result).toEqual({
+    GB: "GBP",
+  });
+});
+
+test("returns an empty object when given an empty array", () => {
+  const countryCurrencyPairs = [];
+
+  const result = createLookup(countryCurrencyPairs);
+
+  expect(result).toEqual({});
+});
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..c825d8cef 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,16 +1,25 @@
 function parseQueryString(queryString) {
-  const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
-  }
-  const keyValuePairs = queryString.split("&");
+  if (queryString === "") {
+    return {};
+  } else {
+    queryString = decodeURIComponent(queryString)
+      .replace(/\+/g, " ")
+      .replace(/&&/g, "&")
+      .replace(/&+$/, "");
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
-  }
+    const splitByAnds = queryString.split("&");
+
+    const splitByEquals = splitByAnds.map(x => {
+      const match = x.match(/^([^=]*)(?:=(.*))?$/);
 
-  return queryParams;
+      const key = match[1];
+      const value = match[2] ?? "";
+
+      return [key, value];
+    });
+
+    return Object.fromEntries(splitByEquals);
+  }
 }
 
 module.exports = parseQueryString;
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 328b8df61..909f04abc 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -37,12 +37,62 @@ test("should replace '+' by ' '", () => {
   });
 });
 
-// Stretch exercise: Handling query strings that contain identical keys
+test("should parse basic key-value pairs", () => {
+  expect(parseQueryString("name=John&age=30")).toEqual({
+    name: "John",
+    age: "30",
+  });
+});
+
+test("should replace '+' by ' '", () => {
+  expect(parseQueryString("name=John+Doe&city=New+York")).toEqual({
+    name: "John Doe",
+    city: "New York",
+  });
+
+  expect(parseQueryString("full+name=John+Doe")).toEqual({
+    "full name": "John Doe",
+  });
+});
+
+test("should decode percent-encoded characters", () => {
+  expect(parseQueryString("message=Hello%20World")).toEqual({
+    message: "Hello World",
+  });
 
-// 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",
+  expect(parseQueryString("%24half=1%2F2")).toEqual({
+    $half: "1/2",
   });
 });
+
+test("should handle keys without values", () => {
+  expect(parseQueryString("debug")).toEqual({
+    debug: "",
+  });
+
+  expect(parseQueryString("key")).toEqual({
+    key: "",
+  });
+});
+
+test("should handle empty values", () => {
+  expect(parseQueryString("name=&age=25")).toEqual({
+    name: "",
+    age: "25",
+  });
+
+  expect(parseQueryString("key=")).toEqual({
+    key: "",
+  });
+});
+
+test("should return empty object for empty input", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("should use the last value when duplicate keys exist", () => {
+  expect(parseQueryString("color=red&color=blue")).toEqual({
+    color: "blue",
+  });
+});
+
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..84b03e706 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,16 @@
-function tally() {}
+function tally(items) {
+  if (!Array.isArray(items)) {
+    throw new TypeError("Input must be an array");
+  }
+
+  const uniqueItems = [...new Set(items)].sort();
+
+  const counts = {};
+  for (const item of uniqueItems) {
+    counts[item] = items.filter(x => x === item).length;
+  }
+
+  return counts;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..ea349000e 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -20,15 +20,36 @@ const tally = require("./tally.js");
 // When passed an array of items
 // Then it should return an object containing the count for each unique item
 
+test("tally counts the frequency of each unique item", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({
+    a: 2,
+    b: 1,
+    c: 1,
+  });
+});
+
 // Given an empty array
 // When passed to tally
 // Then it should return an empty object
-test.todo("tally on an empty array returns an empty object");
+
+test("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
 
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
 
+test("tally counts duplicate items correctly", () => {
+  expect(tally(["a", "a", "a"])).toEqual({
+    a: 3,
+  });
+});
+
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+
+test("tally throws an error when passed invalid input", () => {
+  expect(() => tally("a")).toThrow();
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..f04b2fb08 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -9,8 +9,8 @@
 function invert(obj) {
   const invertedObj = {};
 
-  for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+  for (const [value, key] of Object.entries(obj)) {
+    invertedObj[key] = value;
   }
 
   return invertedObj;
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..fd92c1baf
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,46 @@
+const invert = require("./invert.js");
+
+/*
+Implement a function called invert that swaps the keys and values of an object.
+
+E.g. invert({ x: 10, y: 20 })
+// returns { "10": "x", "20": "y" }
+*/
+
+// Acceptance criteria:
+
+// Given an empty object
+// When passed to invert
+// Then it should return an empty object
+test("returns an empty object when given an empty object", () => {
+  expect(invert({})).toEqual({});
+});
+
+// Given an object with one property
+// When passed to invert
+// Then it should swap the key and value
+test("inverts an object with one key-value pair", () => {
+  expect(invert({ a: 1 })).toEqual({
+    "1": "a",
+  });
+});
+
+// Given an object with multiple properties
+// When passed to invert
+// Then it should swap all keys and values
+test("inverts an object with multiple key-value pairs", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({
+    "1": "a",
+    "2": "b",
+  });
+});
+
+// Given an object with string values
+// When passed to invert
+// Then it should swap the keys and values
+test("inverts string values correctly", () => {
+  expect(invert({ first: "apple", second: "banana" })).toEqual({
+    apple: "first",
+    banana: "second",
+  });
+});