diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index b22590bc6..dbd87e607 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,9 +6,33 @@
 // 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 list is not an array return null.
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  // filter the list to include only valid numbers (excludes Infinity, -Infinity, and NaN)
+  const numbers = list.filter(
+    (item) => typeof item === "number" && Number.isFinite(item)
+  );
+
+  // if numbers array is empty return null.
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  // sort the numbers in the number array in ascending order.
+  numbers.sort((a, b) => a - b);
+
+  // find the middle index and store it in a variable.
+  const middleIndex = Math.floor(numbers.length / 2);
+
+  // if its an even array there are two middle indexes, so add them together and divide by two.
+  if (numbers.length % 2 === 0) {
+    return (numbers[middleIndex] + numbers[middleIndex - 1]) / 2;
+  }
+  // for odd arrays return middle index.
+  return numbers[middleIndex];
 }
 
 module.exports = calculateMedian;
diff --git a/Sprint-1/fix/median.test.js b/Sprint-1/fix/median.test.js
index 21da654d7..c262c3776 100644
--- a/Sprint-1/fix/median.test.js
+++ b/Sprint-1/fix/median.test.js
@@ -13,7 +13,8 @@ describe("calculateMedian", () => {
     { input: [1, 2, 3, 4], expected: 2.5 },
     { input: [1, 2, 3, 4, 5, 6], expected: 3.5 },
   ].forEach(({ input, expected }) =>
-    it(`returns the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`returns the median for [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 
   [
@@ -24,7 +25,8 @@ describe("calculateMedian", () => {
     { input: [110, 20, 0], expected: 20 },
     { input: [6, -2, 2, 12, 14], expected: 6 },
   ].forEach(({ input, expected }) =>
-    it(`returns the correct median for unsorted array [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`returns the correct median for unsorted array [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 
   it("doesn't modify the input array [3, 1, 2]", () => {
@@ -33,8 +35,17 @@ describe("calculateMedian", () => {
     expect(list).toEqual([3, 1, 2]);
   });
 
-  [ 'not an array', 123, null, undefined, {}, [], ["apple", null, undefined] ].forEach(val =>
-    it(`returns null for non-numeric array (${val})`, () => expect(calculateMedian(val)).toBe(null))
+  [
+    "not an array",
+    123,
+    null,
+    undefined,
+    {},
+    [],
+    ["apple", null, undefined],
+  ].forEach((val) =>
+    it(`returns null for non-numeric array (${val})`, () =>
+      expect(calculateMedian(val)).toBe(null))
   );
 
   [
@@ -45,6 +56,7 @@ describe("calculateMedian", () => {
     { input: [3, "apple", 1, null, 2, undefined, 4], expected: 2.5 },
     { input: ["banana", 5, 3, "apple", 1, 4, 2], expected: 3 },
   ].forEach(({ input, expected }) =>
-    it(`filters out non-numeric values and calculates the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`filters out non-numeric values and calculates the median for [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 });
diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 781e8718a..f10b813d2 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1 +1,12 @@
-function dedupe() {}
+function dedupe(elements) {
+  const result = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (!result.includes(elements[i])) {
+      result.push(elements[i]);
+    }
+  }
+
+  return result;
+}
+
+module.exports = dedupe;
diff --git a/Sprint-1/implement/dedupe.test.js b/Sprint-1/implement/dedupe.test.js
index 23e0f8638..8a1a8c871 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -16,12 +16,31 @@ 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", () => {
+  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, it should return a copy of the original array", () => {
+  const input = ["a", "b", "c"];
+  const result = dedupe(input);
 
-// Given an array with strings or numbers
+  expect(result).toHaveLength(input.length);
+  expect(result).toEqual(input);
+  expect(result).not.toBe(input);
+});
+
+// Given an array with strings
 // When passed to the dedupe function
-// Then it should remove the duplicate values, preserving the first occurence of each element
+// Then it should remove duplicates and not modify the original array
+test("given an array with strings, it should remove duplicates and preserve the original array", () => {
+  const input = ["a", "a", "a", "b", "b", "c"];
+  const original = [...input];
+
+  const result = dedupe(input);
+
+  expect(result).toEqual(["a", "b", "c"]);
+  expect(input).toEqual(original);
+});
diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 6dd76378e..e65aa5bc0 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,4 +1,20 @@
 function findMax(elements) {
-}
+  const numbersOnly = elements.filter(
+    (e) => typeof e === "number" && Number.isFinite(e)
+  );
+
+  if (numbersOnly.length === 0) {
+    return -Infinity;
+  }
+
+  let max = numbersOnly[0];
 
+  for (let i = 1; i < numbersOnly.length; i++) {
+    if (numbersOnly[i] > max) {
+      max = numbersOnly[i];
+    }
+  }
+
+  return max;
+}
 module.exports = findMax;
diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index 82f18fd88..05d135a65 100644
--- a/Sprint-1/implement/max.test.js
+++ b/Sprint-1/implement/max.test.js
@@ -16,28 +16,68 @@ 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([])).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([7])).toBe(7);
+});
+
 // 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 positive and negative numbers, returns the largest number", () => {
+  expect(findMax([-3, 7, -2, 5])).toBe(7);
+});
+
 // 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 only negative numbers, returns the closest to zero", () => {
+  expect(findMax([-10, -3, -7])).toBe(-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 clargest decimal number", () => {
+  expect(findMax([2.7, 6.9, 10.1])).toBe(10.1);
+});
+
 // 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 ignore non-numeric values", () => {
+  expect(findMax([3, "dogs", 1, "cat", null])).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 -Infinity", () => {
+  expect(findMax(["a", null, true, undefined])).toBe(-Infinity);
+});
+
+// Given an array with Nan
+// When passed to the max function
+// Then it should return the correct maximum value
+test("given an array including Nan return correct maximum value", () => {
+  expect(findMax([11, NaN, 5])).toBe(11);
+});
+
+// Given an array with numeric string value
+// When passed to the max function
+// Then it should ignore the numeric string and return correct maximum value
+test("given an array with numeric string value, it should ignore the numeric string and return correct maximum value", () => {
+  expect(findMax([8, "14", 2])).toBe(8);
+});
diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 9062aafe3..206f57da2 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,4 +1,12 @@
 function sum(elements) {
+  let total = 0;
+
+  for (let i = 0; i < elements.length; i++) {
+    if (typeof elements[i] === "number" && Number.isFinite(elements[i])) {
+      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..078978add 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -13,24 +13,53 @@ 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([])).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("given an array containing negative numbers", () => {
+  expect(sum([-5, -6, -1])).toBe(-12);
+});
+
 // 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([2.75, -0.3, 0.0002])).toBeCloseTo(2.4502);
+});
+
 // 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, ignore the non-numerical values and return the sum of the numerical elements", () => {
+  expect(sum(["hello", 6, true, 14])).toBe(20);
+});
+
 // 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(["hello", undefined, "today", true])).toBe(0);
+});
+
+// Given an array including NaN
+// When passed to the sum function
+// Then it should ignore the NaN value
+test("given an array that include NaN returns correct answer", () => {
+  expect(sum([7, 14, NaN])).toBe(21);
+});
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;
     }