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..3667ab42f 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -11,6 +11,10 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }
+
+
+// It did work because an object is not iterable as an array, but we can use Object.values() 
+// to get an array of the property values and then iterate over that array.
\ No newline at end of file
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..5e389e417 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -4,12 +4,17 @@
 // Each ingredient should be logged on a new line
 // How can you fix it?
 
+// it won't work because the last line is calling the object property recipe and we
+// need the ingredientes, the console.log is trying to log the whole array of ingredients 
+// as a string, but we want to log each ingredient on a new line. We can fix this by 
+// using a for loop to iterate over the ingredients array and log each ingredient separately.
+
 const recipe = {
-  title: "bruschetta",
+  title: "Bruschetta",
   serves: 2,
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+
+console.log(`Recipe: ${recipe.title} \nserves: ${recipe.serves}`);
+console.log(recipe.ingredients.join("\n"));
\ No newline at end of file
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..5ff840c0a 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,10 @@
-function contains() {}
+function contains(obj, property) {
+    if (typeof obj !== "object" || obj === null || Array.isArray(obj)){
+        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..7f0d07dc7 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -16,20 +16,51 @@ 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("return true when an object has the property name", () => {
+    expect(contains({a: 1, b: 2}, "a")).toBe(true);
+})
 
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("returns false on empty object ", () => {
+    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("return true when pass an object that contains the property name", () => {
+    expect(contains({name: "John", age: 30}, "name")).toBe(true);
+})
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("return false when pass an object that does not contain the property name", () => {
+    expect(contains({id: 12, status: "active"}, "age")).toBe(false);
+})
 
 // Given invalid parameters like an array
-// When passed to contains
+// When: Checking for a valid array property like 'length' or an index
 // Then it should return false or throw an error
+test("return false when pass an array instead of an object", () => {
+    expect(contains(["Banana"], "length")).toBe(false);
+    expect(contains(["Apple"], "0")).toBe(false);
+})
+
+// Given a value that is null, undefined, or a primitive (like 123)
+// When passed to the contains function
+// Then it should return false to prevent errors and ensure only real objects are processed.
+test("should return false for null and other non-objects", () => {
+  expect(contains(null, "prop")).toBe(false);
+  expect(contains(undefined, "prop")).toBe(false);
+  expect(contains(123, "toFixed")).toBe(false);
+});
+
+// Given: A standard object created with literal notation {}.
+// When: It is passed to the 'contains' function looking for a built-in property like "toString".
+// Then: It should return false because the object is not the "owner" of that property.
+test("Should return false for inherited properties like 'toString'", () => {
+  expect(contains({}, "toString")).toBe(false);
+});
\ No newline at end of file
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..dd08c9306 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,9 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  const result = {};
+  for(const [country, currency] of pairs) {
+    result[country] = currency;
+  }
+  return result
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..b6ba7c768 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,5 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
 
 /*
 
@@ -33,3 +32,20 @@ It should return:
    'CA': 'CAD'
  }
 */
+
+test("return an object with country codes as keys and currency codes as values", () => {
+  expect( createLookup([ ["MX", "MXN"], ["JP", "JPY"] ])).toEqual({ MX: "MXN", JP: "JPY"});
+  expect( createLookup([ ["AU", "AUD"], ["CH", "CHF"] ])).toEqual({ AU: "AUD", CH: "CHF" });
+});
+
+describe("return an object with country codes as keys and currency codes as values", () => {
+  [
+    { input: [["US", "USD"],["CA", "CAD"]], expected: { US: "USD", CA: "CAD" } },
+    { input: [["GB", "GBP"],["FR", "EUR"]], expected: { GB: "GBP", FR: "EUR" } },
+    { input: [["JP", "JPY"],["AU", "AUD"]], expected: { JP: "JPY", AU: "AUD" } },
+  ].forEach(({ input, expected }) => {
+    it(`should convert ${JSON.stringify(input)} into ${JSON.stringify(expected)}`, () => {
+      expect(createLookup(input)).toEqual(expected);
+    });
+  });
+});
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..80852a80d 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,15 +1,25 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
+  if (!queryString || queryString.trim() === "" ) {
     return queryParams;
   }
   const keyValuePairs = queryString.split("&");
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
-  }
+  for(const pair of keyValuePairs){
+    if(!pair) continue; 
+  
+    const [key, ...rest] = pair.split("=");
+
+    const value = rest.join("=");
+
+    if (key) {
 
+      const decodedKey = decodeURIComponent(key.replace(/\+/g, " "));
+      const decodedValue = decodeURIComponent(value.replace(/\+/g, " "));
+      queryParams[decodedKey] = decodedValue;
+    }
+
+  }
   return queryParams;
 }
 
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..3341bbc01 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -5,8 +5,53 @@
 
 const parseQueryString = require("./querystring.js")
 
-test("parses querystring values containing =", () => {
-  expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
+
+// Given a querystring with a value that contains an = symbol ( + URL encoded as %2B and spaces encoded as + )
+// When passed to parseQueryString
+// Then it should treat everything after the first = as the value
+test('parses querystring values containing (=, +, " ")', () => {
+  expect(parseQueryString("equation=x=y%2B1")).toEqual({
+    equation: "x=y+1",
+  });
+});
+
+// Given an querystring string with spaces encoded as (%20 and +)
+// when passed to parseQueryString
+// then it should return the string with real spaces in both cases
+test("decodes spaces correctly from both %20 and +", () => {
+  expect(parseQueryString("name=John%20Doe&city=New+York")).toEqual({
+    "name": "John Doe",
+    "city": "New York", 
   });
 });
+
+
+// Given a URL-encoded key like like %5B%5D = []
+// When passed to parseQueryString
+// Then it should decode the key to 'tags[]'
+test("Handles URL-Encoded keys", () =>{
+  expect(parseQueryString("tags%5B%5D=javascript")).toEqual({
+    "tags[]": "javascript",
+  });
+})
+
+// Given a string with multiple ampersands like a=1&&b=2&c=3&&
+// When passed to parseQueryString 
+// Then it should ignore the empty segments and return valid pairs
+test("Should ignore empty ampersand", () => {
+  expect(parseQueryString("a=1&&b=2")).toEqual({
+    a: "1",
+    b: "2",
+
+  });
+})
+
+// Given a key without a value like 'flag' or 'empty='
+// When passed to parseQueryString
+// Then it should return the key with an empty string as value
+test("handles keys with no values", () => {
+  expect(parseQueryString("empty=&flag")).toEqual({
+    "empty": "",
+    "flag": ""
+  });
+});
\ No newline at end of file
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..f5db8d5b5 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,14 @@
-function tally() {}
+function tally(items) {
+  const counts = Object.create(null);
+
+  if (!Array.isArray(items)) {
+    throw new Error("Input must be an array");
+  }
+
+  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..3ef605508 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -19,16 +19,29 @@ 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("Should return an object with the count of each unique item in the array", () => {
+    expect(tally(['a'])).toEqual({ a: 1 });
+    expect(tally(['a', 'a', 'a'])).toEqual({ a: 3 });
+    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("Should return an empty object when passed an empty array", () => {
+    expect(tally([])).toEqual({});
+});
 
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test("Should return counts for each unique item in an array with duplicate items",  () => {
+    expect(tally(['x', 'y', 'x', 'z', 'y', 'x'])).toEqual({ x: 3, y: 2, z: 1 });
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("Should throw and error when passed and invalid input like a string", () => {  
+    expect(() => tally('not an array')).toThrow('Input must be an array');
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..db022ed4a 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -6,24 +6,55 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
+
 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 }
+console.log(invert({ a: 1, b: 2 })); // Expected output: { '1': 'a', '2': 'b' }
+
+
+
+/*
+a) What is the current return value when invert is called with { a : 1 }
+    * is the following { key: 1 }
+
+b) What is the current return value when invert is called with { a: 1, b: 2 }
+    *the first pair is { key: 1 }  
+    *and the second pair the value is  { key: '2' } that means the first pair is 
+    being overwritten by the second pair, so the final return value is { key: '2' }
+
+c) What is the target return value when invert is called with {a : 1, b: 2}
+    *the target return value is { "1": "a", "2": "b" }
+
+d) What does Object.entries return? Why is it needed in this program?
+    *Return value: It returns an array of arrays, where each sub-array is a [key, value] 
+    pair (e.g., [['a', 1]]).
+    *Why it's needed: Objects are not iterables by default. We need Object.entries 
+    to convert the object into an array so we can use the for...of loop to go through each pair.
+
+e) Explain why the current return value is different from the target output
+    *Literal Property Creation: The current code uses dot notation (invertedObj.key), 
+    which creates a property literally named "key" instead of using the value stored 
+    inside the key variable.
+
+    *Overwriting: Because it keeps targetting the same literal property name ("key"), 
+    each iteration overwrites the previous one. This is why the final object only contains 
+    the last value processed.
+
+    *Target vs. Current: The target output requires bracket notation (invertedObj[value]) 
+    to dynamically assign the new keys based on the input's values.
 
-// b) What is the current return value when invert is called with { a: 1, b: 2 }
 
-// c) What is the target return value when invert is called with {a : 1, b: 2}
+f) Fix the implementation of invert (and write tests to prove it's fixed!)
+    expect({ a: 1, b: 2 })toEqual({ '1': 'a', '2': 'b' } ) now is working as expected
 
-// c) What does Object.entries return? Why is it needed in this program?
+**/
 
-// d) Explain why the current return value is different from the target output
 
-// e) Fix the implementation of invert (and write tests to prove it's fixed!)
diff --git a/Sprint-2/stretch/mode.js b/Sprint-2/stretch/mode.js
index 3f7609d79..9f95c1f93 100644
--- a/Sprint-2/stretch/mode.js
+++ b/Sprint-2/stretch/mode.js
@@ -8,22 +8,25 @@
 // refactor calculateMode by splitting up the code
 // into smaller functions using the stages above
 
-function calculateMode(list) {
-  // track frequency of each value
-  let freqs = new Map();
 
-  for (let num of list) {
-    if (typeof num !== "number") {
-      continue;
-    }
+// track frequency of each value
+function getFrequency(list) {
+  let frequency = new Map();
 
-    freqs.set(num, (freqs.get(num) || 0) + 1);
+  for (let num of list) {
+    if (typeof num !== "number") continue;
+    frequency.set(num, (frequency.get(num) || 0) + 1);
   }
+  return frequency;
+}
+
 
-  // Find the value with the highest frequency
+// Find the value with the highest frequency
+function getHighestFrequency(frequency) {
   let maxFreq = 0;
   let mode;
-  for (let [num, freq] of freqs) {
+
+  for (let [num, freq] of frequency) {
     if (freq > maxFreq) {
       mode = num;
       maxFreq = freq;
@@ -33,4 +36,11 @@ function calculateMode(list) {
   return maxFreq === 0 ? NaN : mode;
 }
 
+// The refactored calculateMode using the stages above
+function calculateMode(list) {
+  const frequency = getFrequency(list);
+  return getHighestFrequency(frequency);
+}
+
+
 module.exports = calculateMode;
diff --git a/Sprint-2/stretch/till.js b/Sprint-2/stretch/till.js
index 6a08532e7..ba9ec4e37 100644
--- a/Sprint-2/stretch/till.js
+++ b/Sprint-2/stretch/till.js
@@ -8,24 +8,28 @@ function totalTill(till) {
   let total = 0;
 
   for (const [coin, quantity] of Object.entries(till)) {
-    total += coin * quantity;
+     const coinValue = parseInt(coin);
+    total += coinValue * quantity;
   }
 
-  return `£${total / 100}`;
+  return `£${(total / 100).toFixed(2)}`;
 }
 
-const till = {
-  "1p": 10,
-  "5p": 6,
-  "50p": 4,
-  "20p": 10,
-};
-const totalAmount = totalTill(till);
 
-// a) What is the target output when totalTill is called with the till object
+module.exports = totalTill;
 
-// b) Why do we need to use Object.entries inside the for...of loop in this function?
+/*
 
-// c) What does coin * quantity evaluate to inside the for...of loop?
+a) What is the target output when totalTill is called with the till object
+  ----£4.40 because the total value of the coins in the till is 440 pence, which is equivalent to £4.40.
 
-// d) Write a test for this function to check it works and then fix the implementation of totalTill
+b) Why do we need to use Object.entries inside the for...of loop in this function?
+  ----Object.entries allows us to iterate over the key-value pairs of the till object, 
+  otherwise is an object and we cannot directly iterate over it with a for...of loop.
+
+c) What does coin * quantity evaluate to inside the for...of loop?
+    ----£NaN because the coin values are strings multiplied by numbers, which results in NaN.
+
+d) Write a test for this function to check it works and then fix the implementation of totalTill
+
+**/
\ No newline at end of file
diff --git a/Sprint-2/stretch/till.test.js b/Sprint-2/stretch/till.test.js
new file mode 100644
index 000000000..5a3958a29
--- /dev/null
+++ b/Sprint-2/stretch/till.test.js
@@ -0,0 +1,28 @@
+const totalTill = require("./till.js");
+
+describe("totalTill", () => {
+  test("returns the total amount in pounds for a given till object", () => {
+    const till = {
+      "1p": 10,
+      "5p": 6,
+      "50p": 4,
+      "20p": 10,
+    };
+
+    expect(totalTill(till)).toEqual("£4.40");
+  });
+
+  test("returns £0.00 for an empty till", () => {
+    const emptyTill = {};
+
+    expect(totalTill(emptyTill)).toEqual("£0.00");
+  });
+
+  test("handles tills with only one type of coin", () => {
+    const singleCoinTill = {
+      "10p": 5,
+    };
+
+    expect(totalTill(singleCoinTill)).toEqual("£0.50");
+  });
+});