diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..2aeb91c2d 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -3,6 +3,7 @@
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
+// It is not working because the object properties should be accessed using dot notation or bracket notation.
 
 const address = {
   houseNumber: 42,
@@ -12,4 +13,4 @@ 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..388388184 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,4 +1,8 @@
 // Predict and explain first...
+// The for...of loop is used to iterate over iterable objects like arrays or strings.
+// However, author is a plain object, which is not iterable by default.
+// Therefore, using for...of directly on an object will result in a TypeError.
+// To iterate over the values of an object, we can use Object.values(), Object.keys(), or a for...in loop.  
 
 // 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 +15,10 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
-}
+// for (const value of Object.values(author)) {
+//   console.log(value);
+// }
+
+for (const key in author) {
+  console.log(author[key]);
+}
\ No newline at end of file
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..fa7db05ff 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,8 +1,7 @@
 // Predict and explain first...
 
 // 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?
+// 
 
 const recipe = {
   title: "bruschetta",
@@ -12,4 +11,4 @@ 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..6420a8a14 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,16 @@
-function contains() {}
+
+
+function contains(obj, prop) {
+	if (typeof obj !== 'object' || obj === null || Array.isArray(obj)) {
+		return false;
+	}
+	for (const key in obj) {
+		if (key === prop) {
+			return true;
+		}
+	}
+	return false;
+}
 
 module.exports = contains;
+
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..2d239e028 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -17,19 +17,37 @@ as the object doesn't contains a key of 'c'
 // 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");
+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("contains returns true for existing property", () => {
+	expect(contains({a: 1, b: 2}, 'a')).toBe(true);
+	expect(contains({x: 10, y: 20}, 'y')).toBe(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("contains returns false for non-existent property", () => {
+	expect(contains({a: 1, b: 2}, 'c')).toBe(false);
+	expect(contains({x: 10, y: 20}, 'z')).toBe(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("contains returns false for invalid parameters", () => {
+	expect(contains([], 'a')).toBe(false);
+	expect(contains(null, 'a')).toBe(false);
+	expect(contains(undefined, 'a')).toBe(false);
+	expect(contains(42, 'a')).toBe(false);
+	expect(contains("string", 'a')).toBe(false);
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..dc428475c 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,14 @@
-function createLookup() {
-  // implementation here
+
+function createLookup(pairs) {
+  const lookup = {};
+  if (!Array.isArray(pairs)) return lookup;
+  for (const pair of pairs) {
+    if (Array.isArray(pair) && pair.length === 2) {
+      const [country, currency] = pair;
+      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..86132ad24 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,21 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+
+test("creates a country currency code lookup for multiple codes", () => {
+  const pairs = [['US', 'USD'], ['CA', 'CAD'], ['GB', 'GBP']];
+  const expected = { US: 'USD', CA: 'CAD', GB: 'GBP' };
+  expect(createLookup(pairs)).toEqual(expected);
+});
+
+test("returns empty object for empty input", () => {
+  expect(createLookup([])).toEqual({});
+});
+
+test("ignores invalid pairs", () => {
+  const pairs = [['US', 'USD'], ['CA'], 'random', ['GB', 'GBP']];
+  const expected = { US: 'USD', GB: 'GBP' };
+  expect(createLookup(pairs)).toEqual(expected);
+});
 
 /*
 
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..71267a362 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -6,8 +6,17 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    const parts = pair.split("=");
+    const key = parts[0];
+    
+    if (parts.length === 1) {
+      // No = found, set value to undefined
+      queryParams[key] = undefined;
+    } else {
+      // Join everything after the first = back together
+      const value = parts.slice(1).join("=");
+      queryParams[key] = value;
+    }
   }
 
   return queryParams;
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..487344c5d 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -10,3 +10,42 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+
+test("parses basic single parameter", () => {
+  expect(parseQueryString("name=John")).toEqual({
+    "name": "John",
+  });
+});
+
+test("parses multiple parameters", () => {
+  expect(parseQueryString("name=John&age=30&city=London")).toEqual({
+    "name": "John",
+    "age": "30",
+    "city": "London",
+  });
+});
+
+test("handles empty querystring", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("handles parameters with empty values", () => {
+  expect(parseQueryString("name=&age=30")).toEqual({
+    "name": "",
+    "age": "30",
+  });
+});
+
+test("handles parameters without values (no = sign)", () => {
+  expect(parseQueryString("flag&name=John")).toEqual({
+    "flag": undefined,
+    "name": "John",
+  });
+});
+
+test("handles multiple = signs in value", () => {
+  expect(parseQueryString("formula=a=b=c&x=1")).toEqual({
+    "formula": "a=b=c",
+    "x": "1",
+  });
+});
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..8690954d7 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,12 @@
-function tally() {}
+function tally(items) {
+    if (!Array.isArray(items)) {
+        throw new Error("Invalid input");
+    }
+    const counts = {};
+  for (const item of items) {
+    counts[item] = (counts[item] || 0) + 1;
+  }
+    return counts;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..bd4d3c172 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -19,16 +19,32 @@ const tally = require("./tally.js");
 // 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 returns correct counts for unique items", () => {
+    const items = ['apple', 'banana', 'orange'];
+    const expected = { apple: 1, banana: 1, orange: 1 };
+    expect(tally(items)).toEqual(expected);
+});
 // 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 returns correct counts for duplicate items", () => {
+    const items = ['apple', 'banana', 'apple', 'orange', 'banana', 'apple'];
+    const expected = { apple: 3, banana: 2, orange: 1 };
+    expect(tally(items)).toEqual(expected);
+});
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("tally throws an error for invalid input", () => {
+    expect(() => tally("invalid")).toThrowError("Invalid input");
+    expect(() => tally(123)).toThrowError("Invalid input");
+    expect(() => tally({})).toThrowError("Invalid input");
+    expect(() => tally(null)).toThrowError("Invalid input");
+    expect(() => tally(undefined)).toThrowError("Invalid input");
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..4f738b03f 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -10,20 +10,38 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;  // Previously invertedObj.key = value;  BUG HERE! Fixed: use bracket notation and swap key/value
   }
 
   return invertedObj;
 }
 
 // a) What is the current return value when invert is called with { a : 1 }
+// Answer: { key: 1 }
+// The bug causes it to create a property literally named "key" instead of using the variable value
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// Answer: { key: 2 }
+// It keeps overwriting the same "key" property with each value from the loop
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// Answer: { "1": "a", "2": "b" }
+// The values should become keys, and the keys should become values
 
 // c) What does Object.entries return? Why is it needed in this program?
+// Answer: Object.entries(obj) returns an array of [key, value] pairs.
+// Example: Object.entries({ a: 1, b: 2 }) returns [["a", 1], ["b", 2]]
+// It's needed so we can iterate through both keys AND values of the object at the same time
+// Without Object.entries, we can only loop through keys OR values, not both.
 
 // d) Explain why the current return value is different from the target output
+// Answer: The bug is using dot notation: invertedObj.key = value
+// Dot notation creates a property literally named "key" instead of using the variable's value
+// It should use bracket notation: invertedObj[value] = key
+// Also, it should swap the key and value positions
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+// Fixed! The correct line is: invertedObj[value] = key;
+// Tests have been written in invert.test.js and all pass ✓
+
+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..de75ec281
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,24 @@
+const invert = require('./invert.js');
+
+test('inverts object with single key-value pair', () => {
+  expect(invert({ a: 1 })).toEqual({ "1": "a" });
+});
+
+test('inverts object with multiple key-value pairs', () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ "1": "a", "2": "b" });
+});
+
+test('inverts object with string values', () => {
+  expect(invert({ x: 10, y: 20 })).toEqual({ "10": "x", "20": "y" });
+});
+
+test('inverts object with string keys and values', () => {
+  expect(invert({ name: "Alice", city: "London" })).toEqual({ 
+    "Alice": "name", 
+    "London": "city" 
+  });
+});
+
+test('returns empty object for empty input', () => {
+  expect(invert({})).toEqual({});
+});