diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..ccac56018 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+//This code is using the wrong syntax to access the houseNumber property of the address object. It will therefore return undefined. 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -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..40b981618 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// This program attempts to log out all the property values in the object. its not going to work because we cannot use "for of" loop in this situation. 
 // 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 +11,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+for (const key in author) {
+  console.log(author[key]);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..e15b83f35 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// This program will not log out the ingredients correctly because we are trying to log the whole recipe object instead of 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 +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..758f6667f 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,8 @@
-function contains() {}
+function contains(obj, key) {
+    if (typeof obj !== 'object' || obj === null || Array.isArray(obj)) {
+        return false; 
+    }
+    return Object.hasOwn(obj, key);
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..eec1701f8 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -16,7 +16,8 @@ as the object doesn't contains a key of 'c'
 // 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
-
+test.todo("contains returns true for existing property");
+test.todo("contains returns false for non-existent property");
 // Given an empty object
 // When passed to contains
 // Then it should return false
@@ -25,11 +26,12 @@ 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
-
+test.todo("contains returns true for existing property");
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
-
+test.todo("contains returns false for non-existent property");
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test.todo("contains with invalid parameters returns false or throws error");
\ No newline at end of file
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..0cb505fe7 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,10 @@
-function createLookup() {
+function createLookup(pairs) {
   // implementation here
+  const lookup = {};
+  for (const [country, currency] of 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..a35173d6a 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,9 @@
 const createLookup = require("./lookup.js");
 
 test.todo("creates a country currency code lookup for multiple codes");
+test.todo("creates a country currency code lookup for an empty array");
+test.todo("creates a country currency code lookup for duplicate country codes");
+test.todo("creates a country currency code lookup for invalid input");
 
 /*
 
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..cdd625ae1 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -6,10 +6,15 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    const index = pair.indexOf("=");
+    if (index === -1) {
+      queryParams[pair] = "";
+    } else {
+      const key = pair.substring(0, index);
+      const value = pair.substring(index + 1);
+      queryParams[key] = value;
+    }
   }
-
   return queryParams;
 }
 
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..ecba3f6cb 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -10,3 +10,22 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+test("parses multiple parameters", () => {
+  expect(parseQueryString("a=1&b=2")).toEqual({ a: "1", b: "2" });
+});
+test("parses empty querystring", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+test("parses parameter without value", () => {
+  expect(parseQueryString("flag")).toEqual({ flag: "" });
+});
+test("parses parameter with empty value", () => {
+  expect(parseQueryString("empty=")).toEqual({ empty: "" });
+}); 
+test("parses parameter with multiple =", () => {
+  expect(parseQueryString("data=a=b=c")).toEqual({ data: "a=b=c" });
+});
+test("parses parameter with special characters", () => {
+  expect(parseQueryString("name=John%20Doe&age=30")).toEqual({ name: "John%20Doe", age: "30" });
+});
+
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..85bb80c7f 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,16 @@
-function tally() {}
+function tally(arr) {
+    if (!Array.isArray(arr)) {
+        throw new Error("Input must be an array");
+    }
+    const counts = Object.create(null);
+    for (const item of arr) {
+        if (counts[item] === undefined) {
+            counts[item] = 1;
+        } else {
+            counts[item] = counts[item] + 1;
+        }
+    }
+    return counts;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..80c64442c 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -19,6 +19,7 @@ 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.todo("tally returns correct counts for unique items in an array");
 
 // Given an empty array
 // When passed to tally
@@ -28,7 +29,9 @@ test.todo("tally on an empty array returns an empty object");
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test.todo("tally returns correct counts for duplicate items in an array");
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test.todo("tally with invalid input throws an error");
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..1379efb14 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -17,13 +17,43 @@ function invert(obj) {
 }
 
 // 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?
-
+//It returns an array of [key, value] pairs from the object. It is needed so we can loop over each key/value pair.
 // d) Explain why the current return value is different from the target output
-
+//The .key is incorrect syntax for setting a key in the object. It should be in brackets.
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+function invert(obj) {
+  const invertedObj = {};
+
+  for (const [key, value] of Object.entries(obj)) {
+    invertedObj[value] = key;
+  }
+
+  return invertedObj;
+}
+
+module.exports = invert;
+
+//jest test cases
+const invert = require("./invert.js");
+
+test("inverts a single object", () => {
+  expect(invert({ a: 1 })).toEqual({ "1": "a" });
+});
+
+test("inverts an object with multiple key-value pairs", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ "1": "a", "2": "b" });
+});
+
+test("inverts string values", () => {
+  expect(invert({ a: "hello", b: "world" })).toEqual({ "hello": "a", "world": "b" });
+});
+
+test("inverts an empty object", () => {
+  expect(invert({})).toEqual({});
+});
\ No newline at end of file