diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..caea304ef 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// The problem is this line:15. address is an object not an array.
 // 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..56ddeaaad 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// I think we can not use for ... of loop for objects. Object is not iriterable.
 // 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 +11,10 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+/*for (const value of author) {
+  console.log(value);
+}*/
+
+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..82b72b6b7 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -10,6 +10,13 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
+/*console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe}`);*/
+
+console.log(`${recipe.title} serves ${recipe.serves}`);
+console.log("ingredients:");
+
+for (const ingredient of recipe.ingredients) {
+  console.log(ingredient);
+}
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..c0d7f7ecc 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,9 @@
-function contains() {}
+function contains(object, propertyName) {
+  if (typeof object !== "object" || object === null || Array.isArray(object)) {
+    return false;
+  }
+
+  return object.hasOwnProperty(propertyName);
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..165b128bb 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,16 +20,43 @@ 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({}, "name")).toEqual(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
 
+test("should return true when the property exists", () => {
+  const object = {
+    name: "John",
+    age: 25,
+  };
+
+  expect(contains(object, "name")).toEqual(true);
+});
+
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
 
+test("should return false when the property does not exist", () => {
+  const object = {
+    name: "John",
+    age: 25,
+  };
+
+  expect(contains(object, "city")).toEqual(false);
+});
+
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+
+test("should return false for invalid parameters", () => {
+  expect(contains([], "name")).toEqual(false);
+  expect(contains(null, "name")).toEqual(false);
+  expect(contains("hello", "name")).toEqual(false);
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..5cc215b6e 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,15 @@
-function createLookup() {
+function createLookup(countryCurrencyParis) {
   // implementation here
+  const lookup = {};
+
+  for (const pair of countryCurrencyParis) {
+    const countryCode = pair[0];
+    const currencyCode = pair[1];
+
+    lookup[countryCode] = currencyCode;
+  }
+
+  return lookup;
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..8f8544baa 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
@@ -10,7 +8,7 @@ Acceptance Criteria:
 
 Given
  - An array of arrays representing country code and currency code pairs
-   e.g. [['US', 'USD'], ['CA', 'CAD']]
+   e.g. [['US', 'USD'], ['CA', 'CAD']] 
 
 When
  - createLookup function is called with the country-currency array as an argument
@@ -33,3 +31,55 @@ It should return:
    'CA': 'CAD'
  }
 */
+
+// Given an array of country-currency pairs
+// When createLookup is called
+// Then it should return an object with matching key-value pairs
+test("creates a country currency code lookup for multiple codes", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  const output = createLookup(input);
+
+  expect(output).toEqual({
+    US: "USD",
+    CA: "CAD",
+  });
+});
+
+// Given an empty array
+// When createLookup is called
+// Then it should return an empty object
+test("returns an empty object for an empty array", () => {
+  expect(createLookup([])).toEqual({});
+});
+
+// Given a single country-currency pair
+// When createLookup is called
+// Then it should return an object with one property
+test("creates a lookup for a single code pair", () => {
+  const input = [["GB", "GBP"]];
+
+  expect(createLookup(input)).toEqual({
+    GB: "GBP",
+  });
+});
+
+// Given multiple country-currency pairs
+// When createLookup is called
+// Then it should include all pairs in the result
+test("creates a lookup for several code pairs", () => {
+  const input = [
+    ["GB", "GBP"],
+    ["JP", "JPY"],
+    ["ET", "ETB"],
+  ];
+
+  expect(createLookup(input)).toEqual({
+    GB: "GBP",
+    JP: "JPY",
+    ET: "ETB",
+  });
+});
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..201388821 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -6,8 +6,35 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (pair === "") {
+      continue;
+    }
+
+    const index = pair.indexOf("=");
+
+    let key;
+    let value;
+
+    if (index === -1) {
+      key = pair;
+      value = "";
+    } else {
+      key = pair.slice(0, index);
+      value = pair.slice(index + 1);
+    }
+
+    key = decodeURIComponent(key.replace(/\+/g, " "));
+    value = decodeURIComponent(value.replace(/\+/g, " "));
+
+    if (queryParams.hasOwnProperty(key)) {
+      if (Array.isArray(queryParams[key])) {
+        queryParams[key].push(value);
+      } else {
+        queryParams[key] = [queryParams[key], value];
+      }
+    } else {
+      queryParams[key] = value;
+    }
   }
 
   return queryParams;
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..68af13a7a 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,19 @@
-function tally() {}
+function tally(items) {
+  if (!Array.isArray(items)) {
+    throw new Error("Input must be an array");
+  }
+
+  const counts = {};
+
+  for (const item of items) {
+    if (counts[item]) {
+      counts[item]++;
+    } else {
+      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..e781daea5 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -20,15 +20,42 @@ 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("should return the count for each unique car brand", () => {
+  const cars = ["Toyota", "BMW", "Toyota", "Honda", "BMW", "Toyota"];
+
+  const result = tally(cars);
+
+  expect(result).toEqual({
+    Toyota: 3,
+    BMW: 2,
+    Honda: 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("should count numbers", () => {
+  expect(tally([1, 2, 1, 3, 2, 1])).toEqual({
+    1: 3,
+    2: 2,
+    3: 1,
+  });
+});
+
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+
+test("should throw an error for invalid input", () => {
+  expect(() => tally("hello")).toThrow("Input must be an array");
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..b770b0eab 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -6,7 +6,7 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
-function invert(obj) {
+/*function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
@@ -14,16 +14,29 @@ function invert(obj) {
   }
 
   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?
-
+// Object.entries(obj) returns an array of key-value pairs.
 // d) Explain why the current return value is different from the target output
-
+// The problem is here:invertedObj.key = value;
+//JavaScript thinks "key" is literally the property name.
 // 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;
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..fd230aeab
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,18 @@
+const invert = require("./invert.js");
+
+test("should invert an object with one property", () => {
+  expect(invert({ a: 1 })).toEqual({
+    1: "a",
+  });
+});
+
+test("should invert an object with multiple properties", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({
+    1: "a",
+    2: "b",
+  });
+});
+
+test("should return an empty object when given an empty object", () => {
+  expect(invert({})).toEqual({});
+});