diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index b22590bc6..ccbf9717a 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,9 +6,28 @@
 // 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;
+
+  // first of all, checking if 'list' is an array
+  if (Array.isArray(list)) {
+    
+    const filteredArr = list.filter(x => typeof x === 'number');
+  
+    if (filteredArr.length < 2) {
+      return null;
+    }
+  
+    // using 'spread operator' copies the array without mutating it
+    const sortedList = [...filteredArr].sort((a, b) => a - b);
+  
+    const middleIndex = Math.floor(sortedList.length / 2);
+  
+    if (sortedList.length % 2 === 0) {
+      return (sortedList[middleIndex - 1] + sortedList[middleIndex]) / 2;
+    } else {
+      return sortedList[middleIndex]
+    }
+  }
+  return null;
 }
 
 module.exports = calculateMedian;
diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 781e8718a..f47d5ce9c 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1 +1,13 @@
-function dedupe() {}
+function dedupe(array) {
+    let arr = array.filter((item, index) => {
+
+        // indexOf() returns the first index where that value appears in the array.
+        if (array.indexOf(item) === index) {
+            return item;
+        }
+    })
+
+    return arr;
+}
+
+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..c05c8721b 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -16,12 +16,23 @@ 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("return an empty array for 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("if no duplicates, return the copy of the original array", () => {
+    expect(dedupe([1, 3, 5, 7])).toEqual([1, 3, 5, 7]);
+})
+
 // 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("an array with strings strings or numbers", () => {
+    expect(dedupe([2, 2, 3, 3, 3, "Black", "Black", "Black", "Green"])).toEqual([2, 3, "Black", "Green"]);
+})
diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 6dd76378e..7a5c0054e 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,4 +1,12 @@
 function findMax(elements) {
+    const filteredArr = elements.filter(x => typeof x === 'number');
+
+    if (filteredArr.length == 0) {
+        return -Infinity;
+    }
+
+    // using 'spread sytax'
+    return Math.max(...filteredArr);
 }
 
 module.exports = findMax;
diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index 82f18fd88..7c2f86699 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("returns -Infinity for an empty array", () => {
+    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, should return that number", () => {
+    expect(findMax([8])).toEqual(8);
+    expect(findMax([-5])).toEqual(-5);
+    expect(findMax([0])).toEqual(0);
+})
+
 // Given an array with both positive and negative numbers
 // When passed to the max function
 // Then it should return the largest number overall
 
+test("return the largest number overall", () => {
+    expect(findMax([-8, -4, 0, 4, 8])).toEqual(8);
+    expect(findMax([-3, -2, -1, 4, 2, 3])).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 only negative numbers, should return closest to 0", () => {
+    expect(findMax([-2, -4, -1, -3, -100])).toEqual(-1);
+})
+
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
 
+test("an array with decimal numbers, should return the largest decimal number", () => {
+    expect(findMax([0.1, 0.2, 0.9, 0.8, 0.3, 0.7, 0.4, 0.6])).toEqual(0.9);
+})
+
 // 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("ignore the non-numeric values", () => {
+    expect(findMax(["Blue", 3, "White", "Orange", "Pink"])).toEqual(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("an array with only non-number values", () => {
+    expect(findMax(["Blue", "White", "Orange", "Pink"])).toEqual(-Infinity);
+})
diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 9062aafe3..51a3a0a9e 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,4 +1,9 @@
 function sum(elements) {
+
+    // const filteredArr = elements.filter(x => typeof x === 'number');
+    // return filteredArr.reduce((a, b) => a + b, 0);
+
+    return elements.filter(x => typeof x === 'number').reduce((a, b) => a + b, 0);
 }
 
 module.exports = sum;
diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index dd0a090ca..a6993d202 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -13,24 +13,49 @@ 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("return 0 for an empty array", () => {
+    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, return that number", () => {
+    expect(sum([3])).toEqual(3);
+    expect(sum([-3])).toEqual(-3);
+    expect(sum([0])).toEqual(0);
+})
+
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
 
+test("return the correct total when passed negative numbers", () => {
+    expect(sum([-3, -6, -1])).toEqual(-10);
+})
+
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
+test("decimal number arrays", () => {
+    expect(sum([0.2, 0.4, 0.2])).toEqual(0.8);
+})
 
 // 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("an array with non-numbers", () => {
+    expect(sum([2, "Blue", 3, "Black", "Green"])).toEqual(5);
+})
+
 // 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("an array with non-number values only", () => {
+    expect(sum([true, false, "Black"])).toEqual(0);
+    expect(sum([undefined, null, "Black"])).toEqual(0);
+})
diff --git a/Sprint-1/refactor/includes.js b/Sprint-1/refactor/includes.js
index 29dad81f0..2e1678917 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;
     }
diff --git a/Sprint-1/stretch/aoc-2018-day1/solution.js b/Sprint-1/stretch/aoc-2018-day1/solution.js
index e69de29bb..feb9593b5 100644
--- a/Sprint-1/stretch/aoc-2018-day1/solution.js
+++ b/Sprint-1/stretch/aoc-2018-day1/solution.js
@@ -0,0 +1,3 @@
+function sum(list) {
+    return list.reduce((a, b) => a + b, 0);
+}
\ No newline at end of file