diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..d2809c142 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,8 +1,13 @@
 // Predict and explain first...
-
+I predict that the code will not log out  the housenumber 
+because there is no method declared inside the object to return the object's properties. 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
+when I run the code it give this message as output (My house number is undefined).
+when I changed the console.log declaration to :
+console.log('my house number is' + ' ' + address.houseNumber);
+it give the right output for the house number. 
 
 const address = {
   houseNumber: 42,
@@ -12,4 +17,9 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+// console.log(`My house number is ${address[0]}`);
+console.log('my house number is' + ' ' + address.houseNumber);
+
+when I checked an AI tool it explained that address is an object, not an array.
+So address[0] tries to access a property with the key "0" — which doesn’t exist → undefined.
+to access the houseNumber property we need to use the property name not an index.
diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..59d644c17 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+I predict that the program will not give the property values of the object because the for loop is not correctly calling the values of the auther object .
 // 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 +11,17 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
-}
+// for (const value of author) {
+//   console.log(value);
+// }
+
+let text = " ";
+for (let x in author) {
+  text+= author[x] + "\n ";
+};
+console.log(text);
+
+// or: 
+const values = Object.values(author);
+console.log(values);
+
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..aee3d6c4d 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,4 +1,6 @@
 // Predict and explain first...
+I expect that the program will not log out the right output because the ingridents are not being accssed correctly.
+as the recipe object is being logged out rather than the ingridents. 
 
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
@@ -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..c7a188e23 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,5 @@
-function contains() {}
+function contains(obj, key) {
+    return key in obj;
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..e4c60cf22 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,16 +20,57 @@ 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.todo("contains on empty object returns false");
 
+test("contains an empty object returns false", () => {
+  const obj = {};
+  expect(contains(obj, "a")).toBe(false);
+});
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("contains an object with properties return ture", () => {
+  const obj = { a: 1, b: 2, c: 3 };
+  expect(contains(obj, "a")).toBe(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("contains an object with propreties return false for non-existing property", () => {
+  const obj = { a: 1, b: 2, c: 3 };
+  expect(contains(obj, "d")).toBe(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("contains with invalid parameters return false", () => {
+  const obj = ["a", "b", "c", "d"];
+  expect(contains(obj, "a")).toBe(false);
+});
+
+// Give an error  for null values:
+
+test("contains give an error when obj is null", ()=> {
+  expect((()=> contains(null , "a"))).toThrow();
+});
+//   throw error for undefiend values:
+test("contains give an error when obj is undefined", ()=> {
+  expect((()=> contains(undefined , "a"))).toThrow();
+});
+
+// throw error for non object typs:
+test(" give an error when obj is a number", ()=> {
+expect((()=> contains(123, "a"))).toThrow();
+});
+
+// throw error when obj is a string:
+test(" give an error when obj is a string", ()=> {
+  expect((()=> contains("hello", "a"))).toThrow();
+});
+
+// give error when obj is boolean:
+test(" give an error when obj is a boolean", ()=> {
+  expect((()=> contains(true, "a"))).toThrow();
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..5c120898b 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,5 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  return Object.fromEntries(countryCurrencyPairs);
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..f6b1c33a4 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -33,3 +33,11 @@ It should return:
    'CA': 'CAD'
  }
 */
+test('Create a lookup object of key value pairs from an array of code pairs', ()=>
+{
+  const countryCurrencyPairs = [["US", "USD"], ["CA", "CAD"]];
+  expect(createLookup(countryCurrencyPairs)).toEqual({
+    US: "USD",
+    CA: "CAD"});
+
+});
\ No newline at end of file
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..1ee34343a 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,16 +1,29 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
-  }
-  const keyValuePairs = queryString.split("&");
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+  if (!queryString) return queryParams;
+
+  const pairs = queryString.split("&");
+
+  for (const pair of pairs) {
+    if (!pair) continue;
+
+    const index = pair.indexOf("=");
+
+    let key, value;
+
+    if (index === -1) {
+      key = decodeURIComponent(pair);
+      value = true;
+    } else {
+      key = decodeURIComponent(pair.slice(0, index));
+      value = decodeURIComponent(pair.slice(index + 1));
+    }
+
     queryParams[key] = value;
   }
 
   return queryParams;
 }
 
-module.exports = parseQueryString;
+module.exports = parseQueryString;
\ No newline at end of file
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..19815d900 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -10,3 +10,43 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+// Empty query string: 
+test("parses querystring with empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+// Key without value:
+test("parses querystring handles key without =", () => {
+  expect(parseQueryString("flag")).toEqual({
+    flag: true,
+  });
+});
+
+// Empty value:
+test("parses querystring with empty value", () => {
+  expect(parseQueryString("key=")).toEqual({
+    key: "",
+  });
+});
+
+// Multiple params:
+test("parses querystring with multiple params", () => {
+  expect(parseQueryString("name=John&age=30&city=New+York")).toEqual({
+    name: "John",
+    age: "30",
+    city: "New York"
+  });
+});
+
+// Value containing = :
+test("parses querystring values containing =", () => {
+  expect(parseQueryString("equation=x=y+1")).toEqual({
+    "equation": "x=y+1",
+  });
+});
+
+// Trailing ampersand:
+test("parses querystring with trailing ampersand", () => {
+  expect(parseQueryString("name=John&")).toEqual({
+    name: "John"
+  });
+});
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..3ee2b7767 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 result = {};
+
+  for (let item of items) {
+    if (Object.hasOwn(result, item)) {
+      result[item] += 1;
+    } else {
+      result[item] = 1;
+    }npm TextDecoderStream
+  }
+
+  return result;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..d0cf86fce 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -19,11 +19,17 @@ 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 on an array of items returns an object with counts of each item", () => { 
+    const items = ["a","a","b","c"]
+    expect(tally(items)).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 ("tally on an empty array returns an empty object", () => {
+    const items = [];
+    expect(tally(items)).toEqual({});
+});
 
 // Given an array with duplicate items
 // When passed to tally
@@ -32,3 +38,7 @@ test.todo("tally on an empty array returns an empty object");
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test('tally on invalid input throw an error', ()=> {
+    const items = 'invalid input';
+    expect(() => tally(items)).toThrow();
+})
\ No newline at end of file
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..6af13915e 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -10,20 +10,34 @@ 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 }
-
+the current return value is {key :1}. 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
-
+the current 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 should be {"1": "a", "2" : "b"}.
 // c) What does Object.entries return? Why is it needed in this program?
-
+object.entries() returns an array of key/value pairs of an object. it is needed in this program to loop through the object and access both the key and value at the same Time .
 // d) Explain why the current return value is different from the target output
-
+because using the key element in the loop is not correct. as using it in  this line :    invertedObj.key = value;
+creats a propty called key rather than using it as a variable . it also doesn't swap the key/vlaue . 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+
+test ("invert should swap keys and values in an object with one key and value", ()=> {
+expect(invert({a :1})).toEqual({"1" :"a"})
+});
+
+test ("invert should swap keys and values in an object with multiple keys and values", ()=> {
+expect(invert({a :1, b: 2})).toEqual({"1" :"a", "2" : "b"})
+});
+
+test('invert should return an empty object when given an empty object', ()=> {
+  expect(invert({})).toEqual({});
+});
\ No newline at end of file