diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index b22590bc6..ade66b21c 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,9 +6,25 @@
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  const numericList = list.filter((item) => Number.isFinite(item));
+
+  if (numericList.length === 0) {
+    return null;
+  }
+
+  numericList.sort((a, b) => a - b);
+
+  const middleIndex = Math.floor(numericList.length / 2);
+
+  if (numericList.length % 2 === 0) {
+    return (numericList[middleIndex - 1] + numericList[middleIndex]) / 2;
+  } else {
+    return numericList[middleIndex];
+  }
 }
 
 module.exports = calculateMedian;
diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 781e8718a..f03270f41 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1 +1,19 @@
-function dedupe() {}
+function dedupe(input) {
+  if (!Array.isArray(input)) {
+    return null;
+  }
+
+  const newArray = [];
+
+  for (let i = 0; i < input.length; i++) {
+    const element = input[i];
+    
+    if (!newArray.includes(element)) {
+      newArray.push(element);
+    }
+  }
+
+  return newArray;
+}
+
+module.exports = dedupe;
\ No newline at end of file
diff --git a/Sprint-1/implement/dedupe.test.js b/Sprint-1/implement/dedupe.test.js
index 23e0f8638..2c7e7e35b 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -16,12 +16,32 @@ E.g. dedupe([1, 2, 1]) target output: [1, 2]
 // Given an empty array
 // When passed to the dedupe function
 // Then it should return an empty array
-test.todo("given an empty array, it returns an empty array");
+test("given an empty array, it returns an empty array", () => {
+  const input = [];
+  const result = dedupe(input);
+  expect(result).toEqual([]);
+  expect(result).not.toBe(input); 
+});
 
 // Given an array with no duplicates
 // When passed to the dedupe function
 // Then it should return a copy of the original array
-
+test("given an array with no duplicates, it returns a copy of the original array", () => {
+  const input = [1, 2, 3];
+  const result = dedupe(input);
+  expect(result).toEqual([1, 2, 3]);
+  expect(result).not.toBe(input); 
+});
 // Given an array with strings or numbers
 // When passed to the dedupe function
 // Then it should remove the duplicate values, preserving the first occurence of each element
+test("removes duplicate values, preserving the first occurrence", () => {
+  expect(dedupe(['a', 'a', 'a', 'b', 'b', 'c'])).toEqual(['a', 'b', 'c']);
+  expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+  expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+});
+
+test("returns null for non-array inputs", () => {
+  expect(dedupe("not an array")).toBeNull();
+  expect(dedupe(123)).toBeNull();
+});
\ No newline at end of file
diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 6dd76378e..1393933cb 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,4 +1,15 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    return null;
+  }
+
+  const numericElements = elements.filter((item) => typeof item === "number");
+
+  if (numericElements.length === 0) {
+    return -Infinity;
+  }
+
+  return Math.max(...numericElements);
 }
 
 module.exports = findMax;
diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index 82f18fd88..1f3aeca3d 100644
--- a/Sprint-1/implement/max.test.js
+++ b/Sprint-1/implement/max.test.js
@@ -16,28 +16,53 @@ const findMax = require("./max.js");
 // When passed to the max function
 // Then it should return -Infinity
 // Delete this test.todo and replace it with a test.
-test.todo("given an empty array, returns -Infinity");
+test("given an empty array, returns -Infinity", () => {
+  expect(findMax([])).toEqual(-Infinity);
+});
 
 // Given an array with one number
 // When passed to the max function
 // Then it should return that number
-
+test("given an array with one number, returns that number", () => {
+  expect(findMax([42])).toEqual(42);
+});
 // Given an array with both positive and negative numbers
 // When passed to the max function
 // Then it should return the largest number overall
-
+test("given an array with both positive and negative numbers, returns the largest number overall", () => {
+  expect(findMax([-10, 5, 100, -50, 20])).toEqual(100);
+});
 // Given an array with just negative numbers
 // When passed to the max function
 // Then it should return the closest one to zero
-
+test("given an array with just negative numbers, returns the closest one to zero", () => {
+  expect(findMax([-10, -20, -3, -4])).toEqual(-3);
+});
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
-
+test("given an array with decimal numbers, returns the largest decimal number", () => {
+  expect(findMax([1.5, 10.5, 0.5, 10.4])).toEqual(10.5);
+});
 // Given an array with non-number values
 // When passed to the max function
 // Then it should return the max and ignore non-numeric values
-
+test("given an array with non-number values, returns the max and ignores non-numeric values", () => {
+  expect(findMax(["apple", "banana", 10, "300", 20])).toEqual(20);
+});
 // Given an array with only non-number values
 // When passed to the max function
 // Then it should return the least surprising value given how it behaves for all other inputs
+test("given an array with only non-number values, returns -Infinity", () => {
+  expect(findMax(["apple", "banana", "cherry"])).toEqual(-Infinity);
+});
+
+//test NaN
+test("NaN", () => {
+  expect(findMax([NaN])).toEqual(NaN);
+});
+
+//test with variables
+test("variables", () => {
+  expect(findMax([0, NaN, 1])).toEqual(NaN);
+});
diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 9062aafe3..d8d874edb 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,4 +1,17 @@
 function sum(elements) {
+  if (!Array.isArray(elements)) {
+    return null;
+  }
+
+  let total = 0;
+
+  for (let i = 0; i < elements.length; i++) {
+    if (typeof elements[i] === "number") {
+      total += elements[i];
+    }
+  }
+
+  return total;
 }
 
 module.exports = sum;
diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index dd0a090ca..fe889eec1 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -13,24 +13,47 @@ const sum = require("./sum.js");
 // Given an empty array
 // When passed to the sum function
 // Then it should return 0
-test.todo("given an empty array, returns 0")
+test("given an empty array, returns 0", () => {
+  expect(sum([])).toEqual(0);
+});
 
 // Given an array with just one number
 // When passed to the sum function
 // Then it should return that number
-
+test("given an array with just one number, returns that number", () => {
+  expect(sum([42])).toEqual(42);
+});
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
-
+test("given an array containing negative numbers, returns the correct total sum", () => {
+  expect(sum([10, -20, 5])).toEqual(-5);
+});
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
-
+test("given an array with decimal/float numbers, returns the correct total sum", () => {
+  expect(sum([1.5, 2.5, 3.1])).toBeCloseTo(7.1);
+});
 // Given an array containing non-number values
 // When passed to the sum function
 // Then it should ignore the non-numerical values and return the sum of the numerical elements
-
+test("given an array containing non-number values, returns the sum of the numerical elements", () => {
+  expect(sum([10, "apple", 20, null, 30])).toEqual(60);
+});
 // Given an array with only non-number values
 // When passed to the sum function
 // Then it should return the least surprising value given how it behaves for all other inputs
+test("given an array with only non-number values, returns 0", () => {
+  expect(sum(["apple", "banana", "cherry"])).toEqual(0);
+});
+
+//Test NaN
+test("NaN", () => {
+  expect(sum([NaN, 1])).toEqual(NaN);
+});
+
+//Test Infinity
+test("Infinity", () => {
+  expect(sum([Infinity, -Infinity])).toEqual(NaN);
+});
diff --git a/Sprint-1/refactor/includes.js b/Sprint-1/refactor/includes.js
index 29dad81f0..8c9ae2e66 100644
--- a/Sprint-1/refactor/includes.js
+++ b/Sprint-1/refactor/includes.js
@@ -1,8 +1,7 @@
 // Refactor the implementation of includes to use a for...of loop
 
 function includes(list, target) {
-  for (let index = 0; index < list.length; index++) {
-    const element = list[index];
+  for (const element of list) {
     if (element === target) {
       return true;
     }