diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index 5c5b796e1..2273eb249 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,9 +6,37 @@
 // or contains values that aren't numbers (the function is expected to throw - see the tests).
 
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+  if (list.length === 0) {
+    throw new Error("calculateMedian requires a non-empty array");
+  }
+
+  for (item of list) {
+    if (typeof item === "string") {
+      throw new Error("calculateMedian requires an array of numbers");
+    }
+    if (item === null) {
+      throw new Error("calculateMedian requires an array of numbers");
+    }
+    if (list.includes(undefined)) {
+      throw new Error("calculateMedian requires an array of numbers");
+    }
+  }
+
+  const sorted = list.toSorted((a, b) => a - b);
+  const oddNum = list.length % 2 === 1;
+
+  if (oddNum) {
+    const middleIndex = Math.floor(list.length / 2);
+    return sorted[middleIndex];
+  } else {
+    const middleIndex = Math.floor(list.length / 2);
+    const middle = middleIndex - 1;
+    const median = (sorted[middleIndex] + sorted[middle]) / 2;
+    return median;
+  }
 }
 
 module.exports = calculateMedian;
diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 781e8718a..8999ed2cf 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1 +1,14 @@
-function dedupe() {}
+function dedupe(arr) {
+  if (arr.length === 0) {
+    return arr;
+  }
+  const newArr = [];
+  for (const item of arr) {
+    if (!newArr.includes(item)) {
+      newArr.push(item);
+    }
+  }
+  return newArr;
+}
+
+module.exports = dedupe;
diff --git a/Sprint-1/implement/dedupe.test.js b/Sprint-1/implement/dedupe.test.js
index d7c8e3d8e..fb0ae2dad 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -16,13 +16,24 @@ E.g. dedupe([1, 2, 1]) returns [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, should return a copy of the original array", () => {
+  const original = ["a", 11, "55"];
+  const expected = dedupe(original);
+  expect(expected).toEqual(original);
+  expect(expected).not.toBe(original);
+});
 
 // Given an array of strings or numbers
 // When passed to the dedupe function
-// Then it should return a new array with duplicates removed while preserving the 
+// Then it should return a new array with duplicates removed while preserving the
 // first occurrence of each element from the original array.
+test("given an array of strings and numbers, should return a new array with duplicates removed", () => {
+  expect(dedupe(["a", "a", 33, 33, 1])).toEqual(["a", 33, 1]);
+});
diff --git a/Sprint-1/implement/describe-median.js b/Sprint-1/implement/describe-median.js
index 3381cfc0a..e6a0a4033 100644
--- a/Sprint-1/implement/describe-median.js
+++ b/Sprint-1/implement/describe-median.js
@@ -20,6 +20,13 @@ function calculateMedian(list) {
 }
 
 // Implement this function. See describe-median.test.js for the acceptance criteria.
-function describeMedian(list) {}
+function describeMedian(list) {
+  try {
+    const median = calculateMedian(list);
+    return "The median is " + median;
+  } catch (error) {
+    return "Could not calculate a median: " + error.message;
+  }
+}
 
 module.exports = describeMedian;
diff --git a/Sprint-1/implement/describe-median.test.js b/Sprint-1/implement/describe-median.test.js
index e7d18a264..56a34a674 100644
--- a/Sprint-1/implement/describe-median.test.js
+++ b/Sprint-1/implement/describe-median.test.js
@@ -21,12 +21,27 @@ const describeMedian = require("./describe-median.js");
 // When passed to describeMedian
 // Then it should return "The median is " followed by the median
 // Delete this test.todo and replace it with a test.
-test.todo('given [1, 2, 3], returns "The median is 2"');
+test('given [1, 2, 3], returns "The median is 2"', () => {
+  expect(describeMedian([1, 2, 3])).toEqual("The median is 2");
+});
 
 // Given an empty array
 // When passed to describeMedian
 // Then it should return "Could not calculate a median: calculateMedian requires a non-empty array"
+test('given an empty array,should return "Could not calculate a median: calculateMedian requires a non-empty array"', () => {
+  expect(describeMedian([])).toEqual(
+    "Could not calculate a median: calculateMedian requires a non-empty array"
+  );
+});
 
 // Given something that isn't an array of numbers, e.g. "banana"
 // When passed to describeMedian
 // Then it should return "Could not calculate a median: calculateMedian requires an array of numbers"
+test('given something that is not an array of numbers, should return "Could not calculate a median: calculateMedian requires an array of numbers"', () => {
+  expect(describeMedian(32)).toEqual(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+  expect(describeMedian("banana")).toEqual(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+});
diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 6dd76378e..8d7a48b81 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,4 +1,19 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+  if (elements.includes(NaN)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+  if (elements.length === 0) {
+    return -Infinity;
+  }
+
+  if (elements.length === 1) {
+    return elements[0];
+  }
+  const sortedList = elements.toSorted((a, b) => a - b);
+  return sortedList.at(-1);
 }
 
 module.exports = findMax;
diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index ff3fbb5e5..b7df06eeb 100644
--- a/Sprint-1/implement/max.test.js
+++ b/Sprint-1/implement/max.test.js
@@ -16,28 +16,58 @@ 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([4])).toEqual(4);
+});
 
 // 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, should returns the largest number overall", () => {
+  expect(findMax([4, -2])).toEqual(4);
+});
 
 // 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, should return the closest one to zero", () => {
+  expect(findMax([-2, -54])).toEqual(-2);
+});
 
 // 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, should return the largest decimal number", () => {
+  expect(findMax([3.5, 10.8])).toEqual(10.8);
+});
 
 // Given an array containing a value that isn't a number
 // When passed to the max function
 // Then it should throw Error("findMax requires an array of numbers")
-
+test("throws an error when an array contains a non-number", () => {
+  expect(() => findMax([10, NaN, 22])).toThrow(
+    "findMax requires an array of numbers"
+  );
+});
 // Given something that isn't an array at all, such as "hey", 42 or no argument
 // When passed to the max function
 // Then it should throw Error("findMax requires an array of numbers")
+test("throws an error when input is a string", () => {
+  expect(() => findMax("hello")).toThrow(
+    "findMax requires an array of numbers"
+  );
+});
+
+test("throws an error when input is a number", () => {
+  expect(() => findMax(42)).toThrow("findMax requires an array of numbers");
+});
+
+test("throws an error when no argument is provided", () => {
+  expect(() => findMax()).toThrow("findMax requires an array of numbers");
+});
diff --git a/Sprint-1/implement/mean.js b/Sprint-1/implement/mean.js
index 36909ea1f..dee0001c4 100644
--- a/Sprint-1/implement/mean.js
+++ b/Sprint-1/implement/mean.js
@@ -1,3 +1,26 @@
-function calculateMean(list) {}
+function calculateMean(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+  for (const item of list) {
+    if (typeof item !== "number") {
+      throw new Error("calculateMean requires an array of numbers");
+    }
+  }
+  if (list.length === 0) {
+    throw new Error("calculateMean requires a non-empty array");
+  }
+  if (list.length === 1) {
+    return list[0];
+  }
+
+  let result = 0;
+  let totalItem = 0;
+  for (const item of list) {
+    totalItem += item;
+    result = totalItem / list.length;
+  }
+  return result;
+}
 
 module.exports = calculateMean;
diff --git a/Sprint-1/implement/mean.test.js b/Sprint-1/implement/mean.test.js
index 847b88676..a959e2f77 100644
--- a/Sprint-1/implement/mean.test.js
+++ b/Sprint-1/implement/mean.test.js
@@ -23,28 +23,65 @@ const calculateMean = require("./mean.js");
 // When passed to calculateMean
 // Then it should return their mean
 // Delete this test.todo and replace it with a test.
-test.todo("given [1, 2, 6], returns 3");
+test("given [1, 2, 6], returns 3", () => {
+  expect(calculateMean([1, 2, 6])).toEqual(3);
+});
 
 // Given an array with a single number
 // When passed to calculateMean
 // Then it should return that number
+test("given an array with a single number, should return that number", () => {
+  expect(calculateMean([54])).toEqual(54);
+});
 
 // Given an array containing negative or decimal numbers
 // When passed to calculateMean
 // Then it should return the correct mean
+test("given an array containing negative or decimal numbers, should return the correct mean", () => {
+  expect(calculateMean([-3, 3.6, -10, 2.2])).toEqual(-1.8);
+});
 
 // Given an empty array
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires a non-empty array")
+test("given an empty array,should throw Error(calculateMean requires a non-empty array)", () => {
+  expect(() => calculateMean([])).toThrow(
+    "calculateMean requires a non-empty array"
+  );
+});
 
 // Given a value that isn't an array, e.g. "banana", 42, null or {}
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires an array of numbers")
+test("given a value that is not an array,should throw new Error(calculateMean requires an array of numbers)", () => {
+  expect(() => calculateMean("banana")).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+  expect(() => calculateMean(42)).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+  expect(() => calculateMean(null)).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+  expect(() => calculateMean({})).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});
 
 // Given no argument at all
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires an array of numbers")
+test("given no argument at all, should throw Error(calculateMean requires an array of numbers)", () => {
+  expect(() => calculateMean()).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});
 
 // Given an array containing a non-number value, e.g. [1, "2", 3]
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires an array of numbers")
+test("given an array containing a non-number value, should throw Error(calculateMean requires an array of numbers)", () => {
+  expect(() => calculateMean([1, 5, "13"])).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});
diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 9062aafe3..1597eb352 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,4 +1,21 @@
 function sum(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("sum requires an array of numbers");
+  }
+  if (elements.includes(NaN)) {
+    throw new Error("sum requires an array of numbers");
+  }
+  if (elements.length === 0) {
+    return 0;
+  }
+  if (elements.length === 1) {
+    return elements[0];
+  }
+  let total = 0;
+  for (const item of elements) {
+    total += item;
+  }
+  return total;
 }
 
 module.exports = sum;
diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index a288e0f0a..27c5aee45 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -13,24 +13,48 @@ 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, should return that number", () => {
+  expect(sum([1])).toEqual(1);
+});
 
 // 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,should return the correct total sum", () => {
+  expect(sum([-2, -4, -1])).toEqual(-7);
+});
 
 // 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 wit decimal numbers, should return correct total sum", () => {
+  expect(sum([3.1, 2.1, 8.8])).toEqual(14);
+});
 
 // Given an array containing a value that isn't a number
 // When passed to the sum function
 // Then it should throw Error("sum requires an array of numbers")
+test("given an array containing a value that is not a number, should throw Error(sum requires an array of numbers)", () => {
+  expect(() => sum([NaN, 21])).toThrow("sum requires an array of numbers");
+});
 
 // Given something that isn't an array at all, such as "hey", 42 or no argument
 // When passed to the sum function
 // Then it should throw Error("sum requires an array of numbers")
+test("given something that isn't an array at all, should throw Error(sum requires an array of numbers)", () => {
+  expect(() => sum(21)).toThrow("sum requires an array of numbers");
+});
+
+test("given something that isn't an array at all, should throw Error(sum requires an array of numbers)", () => {
+  expect(() => sum("hello")).toThrow("sum requires an array of numbers");
+});
+test("given something that isn't an array at all, should throw Error(sum requires an array of numbers)", () => {
+  expect(() => sum()).toThrow("sum requires an array of numbers");
+});
diff --git a/Sprint-1/refactor/includes.js b/Sprint-1/refactor/includes.js
index 29dad81f0..6aeac0b5d 100644
--- a/Sprint-1/refactor/includes.js
+++ b/Sprint-1/refactor/includes.js
@@ -1,9 +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];
-    if (element === target) {
+  for (const item of list) {
+    if (item === target) {
       return true;
     }
   }
diff --git a/Sprint-1/stretch/aoc-2018-day1/solution.js b/Sprint-1/stretch/aoc-2018-day1/solution.js
index e69de29bb..1ad8adc19 100644
--- a/Sprint-1/stretch/aoc-2018-day1/solution.js
+++ b/Sprint-1/stretch/aoc-2018-day1/solution.js
@@ -0,0 +1,15 @@
+const fs = require("fs");
+const input = fs.readFileSync("./input.txt", "utf-8");
+
+function calculateFrequency(input) {
+  let frequency = 0;
+  const nums = input.trim().split("\n").map(Number);
+
+  for (num of nums) {
+    frequency += num;
+  }
+  return frequency;
+}
+console.log(calculateFrequency(input));
+
+//529