From 54c6c538c30e44a577811f3dded79dd5adeda77c Mon Sep 17 00:00:00 2001
From: Ali <naru.a@yahoo.com>
Date: Mon, 17 Nov 2025 10:22:13 +0000
Subject: [PATCH 1/7] Refactor: improve median calculation to handle
 non-numeric values and sort correctly

---
 Sprint-1/fix/median.js | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index b22590bc6..aea8f3ce5 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,9 +6,26 @@
 // 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;
+  // Filter only number values
+  const numbers = list.filter((item) => typeof item === "number");
+
+  // Return null if no valid numbers found
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  // Sort numerically (not alphabetically)
+  numbers.sort((a, b) => a - b);
+
+  const middleIndex = Math.floor(numbers.length / 2);
+
+  // Odd number of elements → return the middle one
+  if (numbers.length % 2 !== 0) {
+    return numbers[middleIndex];
+  }
+
+  // Even number → average of the two middle values
+  return (numbers[middleIndex - 1] + numbers[middleIndex]) / 2;
 }
 
 module.exports = calculateMedian;

From 9450fc0d646e2a9426cbf9c48d6da2a5444929ef Mon Sep 17 00:00:00 2001
From: Ali <naru.a@yahoo.com>
Date: Mon, 17 Nov 2025 10:44:14 +0000
Subject: [PATCH 2/7] Refactor: enhance median calculation to ensure input is
 an array and sort without modifying original data

---
 Sprint-1/fix/median.js | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index aea8f3ce5..26435293f 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,26 +6,31 @@
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
 function calculateMedian(list) {
+
+  // First: ensure input is actually an array BEFORE calling array methods
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
   // Filter only number values
   const numbers = list.filter((item) => typeof item === "number");
 
-  // Return null if no valid numbers found
+  // Return null if no valid numbers exist
   if (numbers.length === 0) {
     return null;
   }
 
-  // Sort numerically (not alphabetically)
-  numbers.sort((a, b) => a - b);
-
-  const middleIndex = Math.floor(numbers.length / 2);
+  // Sort values without modifying original input
+  const sortedNumbers = [...numbers].sort((a, b) => a - b);
+  const middleIndex = Math.floor(sortedNumbers.length / 2);
 
-  // Odd number of elements → return the middle one
-  if (numbers.length % 2 !== 0) {
-    return numbers[middleIndex];
+  // Odd length → return middle value
+  if (sortedNumbers.length % 2 !== 0) {
+    return sortedNumbers[middleIndex];
   }
 
-  // Even number → average of the two middle values
-  return (numbers[middleIndex - 1] + numbers[middleIndex]) / 2;
+  // Even length → return average of two middle values
+  return (sortedNumbers[middleIndex - 1] + sortedNumbers[middleIndex]) / 2;
 }
 
 module.exports = calculateMedian;

From f2b76fa732b5b48321d17b8c14b89ed4fc3f33e8 Mon Sep 17 00:00:00 2001
From: Ali <naru.a@yahoo.com>
Date: Tue, 18 Nov 2025 23:49:18 +0000
Subject: [PATCH 3/7] Implement dedupe function and add tests for various
 scenarios

---
 Sprint-1/implement/dedupe.js      | 21 ++++++++++++++++++++-
 Sprint-1/implement/dedupe.test.js | 16 +++++++++++++++-
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 781e8718a..5f74993a0 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1 +1,20 @@
-function dedupe() {}
+function dedupe(arr) {
+    
+  if (!Array.isArray(arr)) return null;
+
+  // Create a new result array
+  const result = [];
+
+  // Loop through original array
+  for (const item of arr) {
+    // Add only the first occurrence of each element
+    if (!result.includes(item)) {
+      result.push(item);
+    }
+  }
+
+  // Return the deduplicated array
+  return result;
+}
+
+module.exports = dedupe;
diff --git a/Sprint-1/implement/dedupe.test.js b/Sprint-1/implement/dedupe.test.js
index 23e0f8638..2daa8447b 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -16,12 +16,26 @@ 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, returns a copy", () => {
+  const arr = [1, 2, 3];
+  const result = dedupe(arr);
+
+  expect(result).toEqual([1, 2, 3]);
+  expect(result).not.toBe(arr); // ensure it's a new array, not the same 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("removes duplicate values 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]);
+});

From 42817a8c52986cb8504bfb62b94157024818295b Mon Sep 17 00:00:00 2001
From: Ali <naru.a@yahoo.com>
Date: Tue, 18 Nov 2025 23:52:09 +0000
Subject: [PATCH 4/7] Refactor: enhance findMax function and add comprehensive
 tests for various scenarios

---
 Sprint-1/implement/max.js      | 11 +++++++++++
 Sprint-1/implement/max.test.js | 22 +++++++++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 6dd76378e..2d82ee2f4 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,4 +1,15 @@
 function findMax(elements) {
+  // If elements is not an array, return -Infinity (least surprising behaviour)
+  if (!Array.isArray(elements)) return -Infinity;
+
+  // Filter numeric values only
+  const numbers = elements.filter((item) => typeof item === "number");
+
+  // If no numeric values found, return -Infinity
+  if (numbers.length === 0) return -Infinity;
+
+  // Return the maximum number
+  return Math.max(...numbers);
 }
 
 module.exports = findMax;
diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index 82f18fd88..3f2585667 100644
--- a/Sprint-1/implement/max.test.js
+++ b/Sprint-1/implement/max.test.js
@@ -16,28 +16,48 @@ 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([42])).toBe(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 mixed positive and negative numbers, returns the largest", () => {
+  expect(findMax([-10, 5, 20, -3])).toBe(20);
+});
 
 // Given an array with just negative numbers
 // When passed to the max function
 // Then it should return the closest one to zero
+test("given only negative numbers, returns the one closest to zero", () => {
+  expect(findMax([-50, -10, -3, -100])).toBe(-3);
+});
 
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
+test("given decimal numbers, returns the largest value", () => {
+  expect(findMax([1.5, 2.7, 2.6, 0.1])).toBe(2.7);
+});
 
 // 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("ignores non-numeric values and returns the maximum number", () => {
+  expect(findMax(["hi", 10, "wow", 30, 5])).toBe(30);
+});
 
 // 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 only non-number values, returns -Infinity", () => {
+  expect(findMax(["a", "b", {}, null])).toBe(-Infinity);
+});

From 94095aa1266a0fca78584ef512bac6563a9526da Mon Sep 17 00:00:00 2001
From: Ali <naru.a@yahoo.com>
Date: Tue, 18 Nov 2025 23:54:22 +0000
Subject: [PATCH 5/7] Refactor: enhance sum function and add comprehensive
 tests for various scenarios

---
 Sprint-1/implement/sum.js      |  7 +++++++
 Sprint-1/implement/sum.test.js | 19 ++++++++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 9062aafe3..4a8c2692d 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,4 +1,11 @@
 function sum(elements) {
+  // If input is not an array, return 0 (least surprising behaviour)
+  if (!Array.isArray(elements)) return 0;
+
+  // Sum only numeric values
+  return elements.reduce((total, item) => {
+    return typeof item === "number" ? total + item : total;
+  }, 0);
 }
 
 module.exports = sum;
diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index dd0a090ca..0ab3313e5 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -13,24 +13,41 @@ 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 one number, returns that number", () => {
+  expect(sum([7])).toBe(7);
+});
 
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
+test("sums negative numbers correctly", () => {
+  expect(sum([-5, -10, 3])).toBe(-12);
+});
 
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
+test("sums decimal numbers correctly", () => {
+  expect(sum([1.5, 2.25, 3.25])).toBe(7);
+});
 
 // 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 and sums only numbers", () => {
+  expect(sum(["hi", 10, "wow", 20, null, 5])).toBe(35);
+});
 
 // 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 only non-number values, returns 0", () => {
+  expect(sum(["a", {}, null, undefined])).toBe(0);
+});

From 692e1dfa4ac16daff47c84cc33b6daf9ea3b21b9 Mon Sep 17 00:00:00 2001
From: Ali <naru.a@yahoo.com>
Date: Tue, 18 Nov 2025 23:56:01 +0000
Subject: [PATCH 6/7] Refactor: simplify includes function by using for...of
 loop

---
 Sprint-1/refactor/includes.js | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

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;
     }

From 4155de416ba0227101d6c06e17531d1ee2c8be7d Mon Sep 17 00:00:00 2001
From: Ali <naru.a@yahoo.com>
Date: Fri, 28 Nov 2025 13:46:49 +0000
Subject: [PATCH 7/7] Refactor: enhance median calculation and improve tests
 for edge cases

---
 Sprint-1/fix/median.js            |  36 ++++++-----
 Sprint-1/fix/median.test.js       |  24 +++++--
 Sprint-1/implement/dedupe.js      |  51 ++++++++++-----
 Sprint-1/implement/dedupe.test.js | 100 +++++++++++++++++++++++-------
 Sprint-1/implement/max.js         |  21 +++----
 Sprint-1/implement/max.test.js    |  50 +++++++++++----
 Sprint-1/implement/sum.js         |  19 +++---
 Sprint-1/implement/sum.test.js    |  35 +++++++----
 Sprint-1/refactor/includes.js     |   6 +-
 9 files changed, 238 insertions(+), 104 deletions(-)

diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index 26435293f..7fea3bdcb 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,31 +6,35 @@
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
 function calculateMedian(list) {
-
-  // First: ensure input is actually an array BEFORE calling array methods
+  // Check that the input passed to the function is an array
   if (!Array.isArray(list)) {
     return null;
   }
 
-  // Filter only number values
-  const numbers = list.filter((item) => typeof item === "number");
+  // Filter valid numbers and store them in `validNumbers`
+  const validNumbers = list.filter(
+    (item) => typeof item === "number" && !isNaN(item)
+  );
 
-  // Return null if no valid numbers exist
-  if (numbers.length === 0) {
+  // Return `null` if there are no valid numbers
+  if (validNumbers.length === 0) {
     return null;
   }
 
-  // Sort values without modifying original input
-  const sortedNumbers = [...numbers].sort((a, b) => a - b);
-  const middleIndex = Math.floor(sortedNumbers.length / 2);
+  // Sort `validNumbers` in ascending order
+  // Sort validNumbers (safe to mutate because it's a new array created by filter)
+  validNumbers.sort((a, b) => a - b);
 
-  // Odd length → return middle value
-  if (sortedNumbers.length % 2 !== 0) {
-    return sortedNumbers[middleIndex];
-  }
+  // Calculate the middle index of the sorted array
+  const middleIndex = Math.floor(validNumbers.length / 2);
 
-  // Even length → return average of two middle values
-  return (sortedNumbers[middleIndex - 1] + sortedNumbers[middleIndex]) / 2;
+  // If the array has an odd number of elements, return the middle element
+  if (validNumbers.length % 2 !== 0) {
+    return validNumbers[middleIndex];
+  } else {
+    // If the array has an even number of elements, return the average of the two middle elements
+    return (validNumbers[middleIndex - 1] + validNumbers[middleIndex]) / 2;
+  }
 }
 
-module.exports = calculateMedian;
+module.exports = calculateMedian;
\ No newline at end of file
diff --git a/Sprint-1/fix/median.test.js b/Sprint-1/fix/median.test.js
index 21da654d7..79da8cd4b 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))
   );
-});
+});
\ No newline at end of file
diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 5f74993a0..24b3de1be 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1,20 +1,43 @@
-function dedupe(arr) {
-    
-  if (!Array.isArray(arr)) return null;
+// This defines a function named dedupe with a parameter arrayInput. arrayInput should be an array.
+function dedupe(arrayInput) {
+  // This checks whether the input is not an array.
+  if (!Array.isArray(arrayInput)) {
+    // If the input is not an array, the function stops, throws a TypeError and shows an error message saying:“Input must be an array.”
+    throw new TypeError("Input must be an array");
+  }
+  // This checks if the array is empty (has no elements).
+  if (arrayInput.length === 0) {
+    // If the array is empty, it returns an empty array.
+    return [];
+  }
+
+  // This declares a new variable `newArray` which will hold a reference to an empty array in memory
+  const newArray = [];
+  // This decares a new varibale `seen` which will hold a reference to the actual set object in memory
+  const seen = new Set(); // variable seen keeps track of all items that have already been added to the result array
+  // seen is a Set object that remembers items,
 
-  // Create a new result array
-  const result = [];
+  // newArray is an array that holds the actual result.
 
-  // Loop through original array
-  for (const item of arr) {
-    // Add only the first occurrence of each element
-    if (!result.includes(item)) {
-      result.push(item);
+  // This starts a loop that goes through each element in the input array one by one.
+  for (const item of arrayInput) {
+    // This big condition checks two things before adding an item:
+
+    // !seen.has(item) — The item has not been added before.
+
+    // The item is either a number (but not NaN) or a string.
+    // So only real numbers and strings that haven’t appeared yet will be kept.
+    if (
+      !seen.has(item) &&
+      ((typeof item === "number" && !Number.isNaN(item)) ||
+        typeof item === "string")
+    ) {
+      newArray.push(item); // If the item passes the condition, it gets added to the new array.
+      seen.add(item); // The item is then recorded in the Set, so it won’t be added again later.
     }
   }
-
-  // Return the deduplicated array
-  return result;
+  // After the loop finishes, return the final deduplicated array
+  return newArray; // After checking all items, the function returns the new array with duplicates removed and invalid items filtered out.
 }
 
-module.exports = dedupe;
+module.exports = dedupe; // This line allows the dedupe function to be used in other files (like the test file).
\ No newline at end of file
diff --git a/Sprint-1/implement/dedupe.test.js b/Sprint-1/implement/dedupe.test.js
index 2daa8447b..ff2e74e3c 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -1,10 +1,11 @@
 const dedupe = require("./dedupe.js");
+
 /*
 Dedupe Array
 
-📖 Dedupe means **deduplicate**
+📖 Dedupe means **dedupe**
 
-In this kata, you will need to deduplicate the elements of an array
+In this kata, you will need to dedupe the elements of an array
 
 E.g. dedupe(['a','a','a','b','b','c']) target output: ['a','b','c']
 E.g. dedupe([5, 1, 1, 2, 3, 2, 5, 8]) target output: [5, 1, 2, 3, 8]
@@ -13,29 +14,80 @@ 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("given an empty array, it returns an empty array", () => {
-  expect(dedupe([])).toEqual([]);
-});
+describe("dedupe - valid inputs", () => {
+  // Given an empty array
+  // When passed to the dedupe function
+  // Then it should return an empty array
+  [{ input: [], expected: [] }].forEach(({ input, expected }) =>
+    test(`returns an empty array for input [${input}]`, () => {
+      const result = dedupe(input);
+      expect(result).toEqual(expected);
+      expect(result).not.toBe(input); // ensures it's a new array
+    })
+  );
 
-// 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", () => {
-  const arr = [1, 2, 3];
-  const result = dedupe(arr);
+  // Given an array with no duplicates
+  // When passed to the dedupe function
+  // Then it should return a copy of the original array
+  [
+    { input: [1, 2, 3], expected: [1, 2, 3] },
+    { input: ["a", "b", "car"], expected: ["a", "b", "car"] },
+    { input: [0, 1, 5, 6], expected: [0, 1, 5, 6] },
+  ].forEach(({ input, expected }) =>
+    test(`returns a copy of the array when no duplicates exist for input [${input}]`, () => {
+      const result = dedupe(input);
+      expect(result).toEqual(expected);
+      expect(result).not.toBe(input); // ensures it's a new array
+    })
+  );
 
-  expect(result).toEqual([1, 2, 3]);
-  expect(result).not.toBe(arr); // ensure it's a new array, not the same reference
-});
+  // Given arrays with duplicates
+  [
+    { input: [5, 1, 1, 2, 3, 2, 5, 8], expected: [5, 1, 2, 3, 8] },
+    { input: [1, 1, 1, 1], expected: [1] },
+    { input: ["a", "a", "a", "b", "b", "c"], expected: ["a", "b", "c"] },
+  ].forEach(({ input, expected }) =>
+    test(`removes duplicate elements and keeps the first occurrence for [${input}]`, () => {
+      const result = dedupe(input);
+      expect(result).toEqual(expected);
+      expect(result).not.toBe(input); // ensures it's a new array
+    })
+  );
 
-// 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 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]);
+  // Given arrays with numbers and strings mixed
+  [
+    { input: ["1", 1, "1", 1], expected: ["1", 1] },
+    { input: [2, "3", "hello", 5, 5], expected: [2, "3", "hello", 5] },
+  ].forEach(({ input, expected }) =>
+    test(`removes duplicates from an array of numbers and strings, keeping the first occurrence for input [${input}]`, () => {
+      const result = dedupe(input);
+      expect(result).toEqual(expected);
+      expect(result).not.toBe(input); // ensures it's a new array
+    })
+  );
+
+  // Given arrays with invalid elements
+  [
+    { input: [1, 2, true, 3, null, "a", {}], expected: [1, 2, 3, "a"] },
+    { input: ["x", undefined, "x", "y", []], expected: ["x", "y"] },
+    { input: [false, 5, 5, "hello", () => {}, 5], expected: [5, "hello"] },
+    { input: [1, NaN, 2, NaN, "hello"], expected: [1, 2, "hello"] },
+  ].forEach(({ input, expected }) =>
+    test(`filters invalid elements, removes duplicates, and returns a copy for input [${input}]`, () => {
+      const result = dedupe(input);
+      expect(result).toEqual(expected);
+      expect(result).not.toBe(input); // ensures it's a new array
+    })
+  );
 });
+
+describe("dedupe - invalid inputs", () => {
+  const invalidInputs = [null, undefined, 123, "string", {}, () => {}];
+
+  invalidInputs.forEach((input) =>
+    test(`throws typeError when input is ${String(input)}`, () => {
+      expect(() => dedupe(input)).toThrow(TypeError);
+      expect(() => dedupe(input)).toThrow("Input must be an array");
+    })
+  );
+});
\ No newline at end of file
diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 2d82ee2f4..28f9b09dc 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,15 +1,12 @@
 function findMax(elements) {
-  // If elements is not an array, return -Infinity (least surprising behaviour)
-  if (!Array.isArray(elements)) return -Infinity;
-
-  // Filter numeric values only
-  const numbers = elements.filter((item) => typeof item === "number");
-
-  // If no numeric values found, return -Infinity
-  if (numbers.length === 0) return -Infinity;
-
-  // Return the maximum number
-  return Math.max(...numbers);
+  if (!Array.isArray(elements)) {
+    throw new TypeError("Input must be an array");
+  } else {
+    const filteredArray = elements.filter(
+      (ele) => typeof ele === "number" && !isNaN(ele)
+    )
+    return Math.max(...filteredArray);
+  }
 }
 
-module.exports = findMax;
+module.exports = findMax;
\ No newline at end of file
diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index 3f2585667..6421a2ab6 100644
--- a/Sprint-1/implement/max.test.js
+++ b/Sprint-1/implement/max.test.js
@@ -24,40 +24,68 @@ test("given an empty array, returns -Infinity", () => {
 // 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])).toBe(42);
+  expect(findMax([8])).toBe(8);
+  expect(findMax([-42])).toBe(-42);
+  expect(findMax([0])).toBe(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("given mixed positive and negative numbers, returns the largest", () => {
-  expect(findMax([-10, 5, 20, -3])).toBe(20);
+test("given an array with both positive and negative numbers, returns the largest number overall", () => {
+  expect(findMax([10, -5, 20, 0])).toBe(20);
+  expect(findMax([-1, -100, -50, 30])).toBe(30);
+  expect(findMax([0, -10, 5])).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 only negative numbers, returns the one closest to zero", () => {
-  expect(findMax([-50, -10, -3, -100])).toBe(-3);
+test("given an array with just negative numbers, returns the closest one to zero", () => {
+  expect(findMax([-10, -5, -20])).toBe(-5);
+  expect(findMax([-100, -50, -60])).toBe(-50);
+  expect(findMax([-1000, -60, -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 decimal numbers, returns the largest value", () => {
-  expect(findMax([1.5, 2.7, 2.6, 0.1])).toBe(2.7);
+test("given an array with decimal numbers, returns the largest decimal number", () => {
+  expect(findMax([1.1, 2.5, 0.3])).toBe(2.5);
+  expect(findMax([-1.2, -0.5, -0.1])).toBe(-0.1);
+  expect(findMax([-1000.23, -80.54, -63.110])).toBe(-63.110);
 });
 
 // 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("ignores non-numeric values and returns the maximum number", () => {
-  expect(findMax(["hi", 10, "wow", 30, 5])).toBe(30);
+test("given an array with non-number values, returns the max and ignore the non-numeric values", () => {
+  expect(findMax([10, "hi", 20, null])).toBe(20);
+  expect(findMax([0, false, 5, "a"])).toBe(5);
+  expect(findMax([undefined, 5, null, NaN, -9])).toBe(5);
 });
 
 // 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 only non-number values, returns -Infinity", () => {
-  expect(findMax(["a", "b", {}, null])).toBe(-Infinity);
+test("given an array with only non-number values", () => {
+  expect(findMax(["a", null, undefined])).toBe(-Infinity);
+  expect(findMax([{}, [], "hi"])).toBe(-Infinity);
+  expect(findMax([true, false, true])).toBe(-Infinity);
+  expect(findMax([Symbol("x"), () => {}, function () {}])).toBe(-Infinity);
 });
+
+// Edge cases
+// Given an array with non-array values
+// when passed to the max function
+// Then it should throw and error
+test("given a non-array input, throws a TypeError with message 'Input must be an array'", () => {
+  expect(() => findMax(42)).toThrow(new TypeError("Input must be an array"));
+  expect(() => findMax("hello")).toThrow(
+    new TypeError("Input must be an array")
+  );
+  expect(() => findMax(null)).toThrow(new TypeError("Input must be an array"));
+  expect(() => findMax(undefined)).toThrow(
+    new TypeError("Input must be an array")
+  );
+});
\ No newline at end of file
diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 4a8c2692d..2cc1c53f8 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,11 +1,16 @@
 function sum(elements) {
-  // If input is not an array, return 0 (least surprising behaviour)
-  if (!Array.isArray(elements)) return 0;
+  if (!Array.isArray(elements)) {
+    throw new TypeError("Input must be an array");
+  }
+  const filteredElements = elements.filter(
+    (ele) => typeof ele === "number" && !isNaN(ele)
+  );
+  let sumElements = 0;
 
-  // Sum only numeric values
-  return elements.reduce((total, item) => {
-    return typeof item === "number" ? total + item : total;
-  }, 0);
+  for (const item of filteredElements) {
+    sumElements += item;
+  }
+  return sumElements;
 }
 
-module.exports = sum;
+module.exports = sum;
\ No newline at end of file
diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index 0ab3313e5..673408c88 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -15,39 +15,52 @@ const sum = require("./sum.js");
 // Then it should return 0
 test("given an empty array, returns 0", () => {
   expect(sum([])).toBe(0);
+
+  const arr = [];
+  expect(sum(arr)).toBe(0);
 });
 
 // Given an array with just one number
 // When passed to the sum function
 // Then it should return that number
-test("given one number, returns that number", () => {
-  expect(sum([7])).toBe(7);
+test("given one number in an array, returns that number", () => {
+  expect(sum([5])).toBe(5);
+  expect(sum([-3])).toBe(-3);
+  expect(sum([0])).toBe(0);
 });
 
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
-test("sums negative numbers correctly", () => {
-  expect(sum([-5, -10, 3])).toBe(-12);
+test("given an array containing negative numbers, should return the correct total sum", () => {
+  expect(sum([-5, -9, -100])).toBe(-114);
+  expect(sum([-1000, -2000, -3000])).toBe(-6000);
+  expect(sum([-1, -2, -3])).toBe(-6);
 });
 
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
-test("sums decimal numbers correctly", () => {
-  expect(sum([1.5, 2.25, 3.25])).toBe(7);
+test("given an array with decimal/float numbers, should return the correct total number", () => {
+  expect(sum([-8.24, 5.46, 3.22])).toBeCloseTo(0.44);
+  expect(sum([-2.5, 2.5, 5.25])).toBeCloseTo(5.25);
+  expect(sum([1.11, 2.22, 3.33])).toBeCloseTo(6.66);
 });
 
 // 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 and sums only numbers", () => {
-  expect(sum(["hi", 10, "wow", 20, null, 5])).toBe(35);
+test("given an array containing non-number values, should ignore the non-numerical values and return the sum of the numerical elements", () => {
+  expect(sum([5, -18, 5.601, null, "kettle"])).toBeCloseTo(-7.4);
+  expect(sum([true, false, 10, -5])).toBe(5);
+  expect(sum([null, 4, 6, "test"])).toBe(10);
 });
 
 // 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 only non-number values, returns 0", () => {
-  expect(sum(["a", {}, null, undefined])).toBe(0);
-});
+test("given an array with only non-number values, should return 0", () => {
+  expect(sum(["food", null, false, true])).toBe(0);
+  expect(sum(["apple", "banana", null, undefined])).toBe(0);
+  expect(sum([NaN, NaN, NaN])).toBe(0);
+});
\ No newline at end of file
diff --git a/Sprint-1/refactor/includes.js b/Sprint-1/refactor/includes.js
index 8c9ae2e66..f984c75bd 100644
--- a/Sprint-1/refactor/includes.js
+++ b/Sprint-1/refactor/includes.js
@@ -1,12 +1,12 @@
 // Refactor the implementation of includes to use a for...of loop
 
 function includes(list, target) {
-  for (const element of list) {
-    if (element === target) {
+  for (const item of list) {
+    if (item === target) {
       return true;
     }
   }
   return false;
 }
 
-module.exports = includes;
+module.exports = includes;
\ No newline at end of file