diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..4f2fa6614 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,5 +1,7 @@
 // Predict and explain first...
 
+// Trying to access the address object using array notation `address[0]` instead of the property name `address.houseNumber`.
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +14,4 @@ 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..06be49433 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,5 +1,9 @@
 // Predict and explain first...
 
+// For..of loop only supports iterable objects (arrays), not objects
+// Should use For..in instead
+// Value needs to be accessed from the object using bracket notation
+
 // This program attempts to log out all the property values in the object.
 // But it isn't working. Explain why first and then fix the problem
 
@@ -11,6 +15,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+for (const value in author) {
+  console.log(author[value]);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..b70698350 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,5 +1,7 @@
 // Predict and explain first...
 
+// Logging the entire recipe object instead of iterating through each element in the ingredients array
+
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
 // How can you fix it?
@@ -12,4 +14,4 @@ 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..c61232cca 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,9 @@
-function contains() {}
+function contains(obj, property) {
+  if (obj === null || obj === undefined) {
+    return false;
+  }
+
+  return Object.hasOwn(obj, property);
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..f5ed844d9 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -1,35 +1,25 @@
 const contains = require("./contains.js");
 
-/*
-Implement a function called contains that checks an object contains a
-particular property
-
-E.g. contains({a: 1, b: 2}, 'a') // returns true
-as the object contains a key of 'a'
-
-E.g. contains({a: 1, b: 2}, 'c') // returns false
-as the object doesn't contains a key of 'c'
-*/
-
-// Acceptance criteria:
-
-// Given a contains function
-// When passed an object and a property name
-// Then it should return true if the object contains the property, false otherwise
-
-// Given an empty object
-// When passed to contains
-// Then it should return false
-test.todo("contains on empty object returns false");
-
-// Given an object with properties
-// When passed to contains with an existing property name
-// Then it should return true
-
-// Given an object with properties
-// When passed to contains with a non-existent property name
-// Then it should return false
-
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error
+describe("contains", () => {
+  test("contains returns true for existing property", () => {
+    expect(contains({ a: 1, b: 2 }, "a")).toBe(true);
+    expect(contains({ a: 1, b: 2 }, "c")).toBe(false);
+  });
+
+  test("contains on empty object returns false", () => {
+    expect(contains({}, "a")).toBe(false);
+  });
+
+  test("contains returns true for multiple properties", () => {
+    expect(contains({ name: "John", age: 30, city: "NY" }, "age")).toBe(true);
+  });
+
+  test("contains returns false for non-existent property", () => {
+    expect(contains({ a: 1, b: 2 }, "c")).toBe(false);
+  });
+
+  test("contains returns false for non-object types", () => {
+    expect(contains(null, "a")).toBe(false);
+    expect(contains(undefined, "a")).toBe(false);
+  });
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..c62cd5935 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,5 @@
-function createLookup() {
-  // implementation here
+function createLookup(arr) {
+  return Object.fromEntries(arr);
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..eb623f2a4 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,35 +1,24 @@
 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
-
-Acceptance Criteria:
-
-Given
- - An array of arrays representing country code and currency code pairs
-   e.g. [['US', 'USD'], ['CA', 'CAD']]
-
-When
- - createLookup function is called with the country-currency array as an argument
-
-Then
- - It should return an object where:
- - The keys are the country codes
- - The values are the corresponding currency codes
-
-Example
-Given: [['US', 'USD'], ['CA', 'CAD']]
-
-When
-createLookup(countryCurrencyPairs) is called
-
-Then
-It should return:
- {
-   'US': 'USD',
-   'CA': 'CAD'
- }
-*/
+describe("createLookup", () => {
+  test("creates a country currency code lookup for multiple codes", () => {
+    const input = [
+      ["US", "USD"],
+      ["CA", "CAD"],
+    ];
+    const result = createLookup(input);
+    expect(result).toEqual({ US: "USD", CA: "CAD" });
+  });
+
+  test("creates a lookup with a single code pair", () => {
+    const input = [["GB", "GBP"]];
+    const result = createLookup(input);
+    expect(result).toEqual({ GB: "GBP" });
+  });
+
+  test("creates an empty lookup with an empty array", () => {
+    const input = [];
+    const result = createLookup(input);
+    expect(result).toEqual({});
+  });
+});
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..32b8c54af 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -6,8 +6,10 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    const [key, ...valueParts] = pair.split("=");
+    const decodedKey = decodeURIComponent(key);
+    const decodedValue = decodeURIComponent(valueParts.join("="));
+    queryParams[decodedKey] = decodedValue;
   }
 
   return queryParams;
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..82628b2e0 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -3,10 +3,29 @@
 // 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.
 
-const parseQueryString = require("./querystring.js")
+const parseQueryString = require("./querystring.js");
 
 test("parses querystring values containing =", () => {
   expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
+    equation: "x=y+1",
   });
 });
+
+test("handles empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("handles key without value", () => {
+  expect(parseQueryString("key1=value1&key2=&key3=value3")).toEqual({
+    key1: "value1",
+    key2: "",
+    key3: "value3",
+  });
+});
+
+test("should decode URL-encoded query strings", () => {
+  const queryString = "tags%5B%5D=hello%20world";
+  const expected = { "tags[]": "hello world" };
+  const result = parseQueryString(queryString);
+  expect(result).toEqual(expected);
+});
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..9578cb2fe 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,18 @@
-function tally() {}
+function tally(arr) {
+  if (!Array.isArray(arr)) {
+    throw new Error();
+  }
+
+  let result = Object.create(null);
+
+  for (const element of arr) {
+    if (element in result) {
+      result[element] += 1;
+    } else {
+      result[element] = 1;
+    }
+  }
+  return result;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..499068667 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -1,34 +1,28 @@
 const tally = require("./tally.js");
 
-/**
- * tally array
- *
- * In this task, you'll need to implement a function called tally
- * that will take a list of items and count the frequency of each item
- * in an array
- *
- * For example:
- *
- * tally(['a']), target output: { a: 1 }
- * tally(['a', 'a', 'a']), target output: { a: 3 }
- * tally(['a', 'a', 'b', 'c']), target output: { a : 2, b: 1, c: 1 }
- */
+describe("tally", () => {
+  test("tally on an empty array returns an empty object", () => {
+    expect(tally([])).toEqual({});
+  });
 
-// Acceptance criteria:
+  test("tally with single item returns object with count of 1", () => {
+    expect(tally(["a"])).toEqual({ a: 1 });
+  });
 
-// Given a function called tally
-// When passed an array of items
-// Then it should return an object containing the count for each unique item
+  test("tally with multiple  items returns counts for each", () => {
+    expect(tally(["a", "a", "a"])).toEqual({ a: 3 });
+    expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 1 });
+    expect(tally(["x", "y", "x", "z", "y", "x"])).toEqual({ x: 3, y: 2, z: 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 with invalid input throws an error", () => {
+    expect(() => tally("invalid")).toThrow();
+    expect(() => tally(null)).toThrow();
+    expect(() => tally(undefined)).toThrow();
+  });
 
-// Given an array with duplicate items
-// When passed to tally
-// Then it should return counts for each unique item
-
-// Given an invalid input like a string
-// When passed to tally
-// Then it should throw an error
+  test("tally returns an object with no inherited properties", () => {
+    const result = tally(["a", "b", "a"]);
+    expect(Object.getPrototypeOf(result)).toBeNull();
+  });
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..6557bd307 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -10,20 +10,28 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
 // a) What is the current return value when invert is called with { a : 1 }
+// { key: 1 }
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// { key: 2 }
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// { 1: "a", 2: "b" }
 
 // c) What does Object.entries return? Why is it needed in this program?
+// Returns an array of key/values of the given object
+// It is needed so that both the key and value can be destructured from the object and reassigned in the for..of loop
 
 // d) Explain why the current return value is different from the target output
+// Dot notation is being used in the for..of loop, bracket notation should be used instead as it will become a computed property
+// value and key should also be swapped inside the for..of loop
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+module.exports = invert;
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..262abf372
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,27 @@
+const invert = require("./invert.js");
+
+describe("invert", () => {
+  test("inverts an empty object", () => {
+    const input = {};
+    const result = invert(input);
+    expect(result).toEqual({});
+  });
+
+  test("inverts a single key-value pair", () => {
+    const input = { a: 1 };
+    const result = invert(input);
+    expect(result).toEqual({ 1: "a" });
+  });
+
+  test("inverts multiple key-value pairs", () => {
+    const input = { a: 1, b: 2 };
+    const result = invert(input);
+    expect(result).toEqual({ 1: "a", 2: "b" });
+  });
+
+  test("inverts an object with string values", () => {
+    const input = { x: "hello", y: "world" };
+    const result = invert(input);
+    expect(result).toEqual({ hello: "x", world: "y" });
+  });
+});