diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index b22590bc6..c67461d6c 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,9 +6,31 @@
 // 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;
+  // Check if list is a valid array
+  if (!Array.isArray(list) || list.length === 0) {
+    return null;
+  }
+
+  // Filter only numeric values (numbers, not NaN, not null, not undefined)
+  const numbers = list.filter(item => typeof item === 'number' && !isNaN(item));
+
+  // If no valid numbers found, return null
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  // Sort the numbers in ascending order (don't mutate original array)
+  const sorted = [...numbers].sort((a, b) => a - b);
+
+  const middleIndex = Math.floor(sorted.length / 2);
+
+  // If odd length, return the middle element
+  if (sorted.length % 2 === 1) {
+    return sorted[middleIndex];
+  }
+
+  // If even length, return the average of the two middle elements
+  return (sorted[middleIndex - 1] + sorted[middleIndex]) / 2;
 }
 
 module.exports = calculateMedian;
diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 781e8718a..744be3fd2 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1 +1,15 @@
-function dedupe() {}
+
+function dedupe(arr) {
+	if (!Array.isArray(arr)) return [];
+	const seen = new Set();
+	const result = [];
+	for (const item of arr) {
+		if (!seen.has(item)) {
+			seen.add(item);
+			result.push(item);
+		}
+	}
+	return result;
+}
+
+module.exports = dedupe;
diff --git a/Sprint-1/implement/dedupe.test.js b/Sprint-1/implement/dedupe.test.js
index 23e0f8638..9d7b6a64f 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -13,15 +13,35 @@ E.g. dedupe([1, 2, 1]) target output: [1, 2]
 
 // Acceptance Criteria:
 
+
 // 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", () => {
+	expect(dedupe([])).toEqual([]);
+});
 
 // 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, returns a copy of the original array", () => {
+	expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+	expect(dedupe(["a", "b", "c"])).toEqual(["a", "b", "c"]);
+
+	// Reference copy check
+	const original = [7, 8, 9];
+	const result = dedupe(original);
+	expect(result).toEqual(original);      // same values
+	expect(result).not.toBe(original);     // different reference
+
+});
 
 // 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("given an array with duplicates, removes duplicates and preserves 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]);
+	expect(dedupe(["x", "y", "x", "z", "y", "x"])).toEqual(["x", "y", "z"]);
+});
diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 6dd76378e..4a6513bc8 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,4 +1,22 @@
 function findMax(elements) {
-}
+    // Filter only numeric values (numbers, not NaN, not null, not undefined)
+    const numbers = elements.filter(function(item) {
+        return typeof item === 'number' && !isNaN(item);
+    });
+
+    // Treat no numbers the same as empty input
+    if (numbers.length === 0) {
+        return -Infinity;
+    }
 
+    // Find the maximum number
+    let max = numbers[0];
+    for (let i = 1; i < numbers.length; i++) {
+        if (numbers[i] > max) {
+            max = numbers[i];
+        }
+    }
+    return max;
+}
+    
 module.exports = findMax;
diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index 82f18fd88..922a2b31f 100644
--- a/Sprint-1/implement/max.test.js
+++ b/Sprint-1/implement/max.test.js
@@ -15,29 +15,59 @@ const findMax = require("./max.js");
 // Given an empty array
 // 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([])).toBe(-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([5])).toBe(5);
+  expect(findMax([42])).toBe(42);
+  expect(findMax([-10])).toBe(-10);
+});
 
 // 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 positive and negative numbers, returns the largest", () => {
+  expect(findMax([30, 50, 10, 40])).toBe(50);
+  expect(findMax([10, -5, 20, -15, 8])).toBe(20);
+  expect(findMax([-3, 5, -10, 2])).toBe(5);
+});
 
 // 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 to zero", () => {
+  expect(findMax([-5, -10, -3, -20])).toBe(-3);
+  expect(findMax([-100, -50, -1])).toBe(-1);
+});
 
 // 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", () => {
+  expect(findMax([3.5, 2.1, 4.8, 1.2])).toBe(4.8);
+  expect(findMax([0.1, 0.9, 0.5])).toBe(0.9);
+  expect(findMax([10.5, 10.7, 10.3])).toBe(10.7);
+});
 
 // 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, ignores them and returns max", () => {
+  expect(findMax(["hey", 10, "hi", 60, 10])).toBe(60);
+  expect(findMax([5, "hello", 15, null, 10, undefined])).toBe(15);
+  expect(findMax([1, "test", 2, NaN, 3])).toBe(3);
+});
 
 // 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 null", () => {
+  expect(findMax(["hello", "world"])).toBe(null);
+  expect(findMax([null, undefined, NaN])).toBe(null);
+  expect(findMax(["a", "b", "c"])).toBe(null);
+});
diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 9062aafe3..e73c36f8e 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,4 +1,12 @@
-function sum(elements) {
+function sum(list) {
+  if (!Array.isArray(list)) return 0;
+  let total = 0;
+  for (const item of list) {
+    if (typeof item === 'number' && !isNaN(item)) {
+      total += item;
+    }
+  }
+  return total;
 }
 
 module.exports = sum;
diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index dd0a090ca..d5355d318 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -8,29 +8,44 @@ E.g. sum(['hey', 10, 'hi', 60, 10]), target output: 80 (ignore any non-numerical
 
 const sum = require("./sum.js");
 
-// Acceptance Criteria:
-
 // 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([])).toBe(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 one number, returns that number", () => {
+  expect(sum([42])).toBe(42);
+});
 
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
+test("sums arrays with negative numbers", () => {
+  expect(sum([10, -5, -15, 20])).toBe(10);
+});
 
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
+test("sums arrays with decimal numbers", () => {
+  expect(sum([1.5, 2.25, 3.25])).toBeCloseTo(7.0);
+});
 
 // 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("ignores non-number values", () => {
+  expect(sum(["a", 10, null, 5, "7", undefined, NaN, 3])).toBe(18);
+});
 
 // 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("array with only non-number values returns 0", () => {
+  expect(sum(["x", null, undefined, "y"])).toBe(0);
+});
diff --git a/Sprint-1/refactor/includes.js b/Sprint-1/refactor/includes.js
index 29dad81f0..bb729c458 100644
--- a/Sprint-1/refactor/includes.js
+++ b/Sprint-1/refactor/includes.js
@@ -1,8 +1,8 @@
 // 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;
     }