From 3fb57efb06f2219d8506693f29386ffe48cd2f91 Mon Sep 17 00:00:00 2001
From: Mouawia Elkhalifa <moawia115@hotmail.com>
Date: Mon, 23 Mar 2026 14:13:27 +0000
Subject: [PATCH 1/4] Complete Sprint 2 exercises

---
 Sprint-2/debug/address.js           |  2 +-
 Sprint-2/debug/author.js            |  2 +-
 Sprint-2/debug/recipe.js            |  4 +--
 Sprint-2/implement/contains.js      |  8 ++++-
 Sprint-2/implement/contains.test.js | 15 ++++++--
 Sprint-2/implement/lookup.js        | 12 +++++--
 Sprint-2/implement/lookup.test.js   |  9 ++++-
 Sprint-2/implement/querystring.js   |  9 +++--
 Sprint-2/implement/tally.js         | 27 +++++++++++++--
 Sprint-2/implement/tally.test.js    | 18 ++++++++--
 Sprint-2/interpret/invert.js        | 54 ++++++++++++++++++++++++-----
 11 files changed, 136 insertions(+), 24 deletions(-)

diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..36d2f865d 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -12,4 +12,4 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address.houseNumber}`);
diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..7ba8f4c75 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -11,6 +11,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..7b93b17b8 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -11,5 +11,5 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:
+${recipe.ingredients.join("\n")}`);
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..81e8e7fab 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,9 @@
-function contains() {}
+function contains(obj, prop) {
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    return false;
+  }
+
+  return prop in obj;
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..26f1d8d4c 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,16 +20,27 @@ as the object doesn't contains a key of 'c'
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("contains on empty object returns false", () =>{
+    expect(contains({}, "a")).toEqual(false)
+});
+
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("contains an object with propery  exist, returns true", () =>{
+    expect(contains({a:1, b:2}, "a")).toEqual(true)
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
-
+test("return false when the property does not exist", () =>{
+    expect(contains({a:1, b:3}, "c")).toEqual(false)
+});
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("return false when paramters invaliud ", () =>{
+    expect(contains([], "a")).toEqual(false)
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..f8253d2c4 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,13 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  const lookup = {};
+
+  for (const [countryCode, countryCurrency] of countryCurrencyPairs) {
+    lookup[countryCode] = countryCurrency;
+  }
+
+  return lookup;
 }
 
 module.exports = createLookup;
+
+
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..b9538744e 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,13 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+test("creates a country currency code lookup for multiple codes",() =>{
+  expect(createLookup([["US", "USD"], ["CA", "CAD"]])).toEqual(
+    {"US":"USD",
+      "CA": "CAD"
+
+  })
+
+})
 
 /*
 
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..7453d4cb3 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,13 +1,18 @@
 function parseQueryString(queryString) {
+  if (queryString.startsWith("?")) {
+    queryString = queryString.substring(1);
+  }
+
   const queryParams = {};
   if (queryString.length === 0) {
     return queryParams;
   }
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    const [key, ...valueParts] = pair.split("=");
+    queryParams[key] = valueParts.join("=");
   }
 
   return queryParams;
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..1f3b66638 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,26 @@
-function tally() {}
+function tally(arr) {
+  //  invalid input → throw error
+  if (!Array.isArray(arr)) {
+    throw new Error("Input must be an array");
+  }
 
-module.exports = tally;
+  //  empty array → return empty object
+  if (arr.length === 0) {
+    return {};
+  }
+
+  const result = {};
+
+  //  count items
+  for (const item of arr) {
+    if (result[item] === undefined) {
+      result[item] = 1;
+    } else {
+      result[item] = result[item] + 1;
+    }
+  }
+
+  return result;
+}
+
+module.exports = tally;
\ No newline at end of file
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..8632463f3 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -18,17 +18,31 @@ const tally = require("./tally.js");
 
 // Given a function called tally
 // When passed an array of items
-// Then it should return an object containing the count for each unique item
+// Then it should return an object containing the count for each unique ite
 
 // Given an empty array
 // When passed to tally
 // Then it should return an empty object
-test.todo("tally on an empty array returns an empty object");
+test("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
+
 
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test("tally counts duplicate items correctly", () => {
+  expect(tally(['a', 'a', 'b', 'c'])).toEqual({
+    a: 2,
+    b: 1,
+    c: 1
+  });
+});
+
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("tally throws an error for invalid input", () => {
+  expect(() => tally("hello")).toThrow();
+});
\ No newline at end of file
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..8fd6f05f0 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -5,25 +5,63 @@
 // Then it should swap the keys and values in the object
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
-
 function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    if (invertedObj[value] === undefined) {
+      invertedObj[value] = key;
+    } else if (Array.isArray(invertedObj[value])) {
+      invertedObj[value].push(key);
+    } else {
+      invertedObj[value] = [invertedObj[value], key];
+    }
   }
 
   return invertedObj;
 }
-
 // a) What is the current return value when invert is called with { a : 1 }
-
+//{"1": "a"}.
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
-
+//{"1": "a", "2": "b"}
 // c) What is the target return value when invert is called with {a : 1, b: 2}
-
+//{"1": "a", "2": "b"}
 // c) What does Object.entries return? Why is it needed in this program?
+// Object.entries(obj) returns an array of [key, value] pairs, where each pair is stored as an array. 
+// It is needed in this program so we can loop through both the keys and values of the object at the same time when inverting it.
+//it returns an array of arrays, where each inner array is a pair: [key, value].
+//The current return value is different from the target output because when multiple keys have
+// the same value, they overwrite each other when inverted. This causes some values to be lost.
+// e) Fix the implementation of invert (and write tests to prove it's fixed!)
+function invert(obj) {
+  const invertedObj = {};
 
-// d) Explain why the current return value is different from the target output
+  for (const [key, value] of Object.entries(obj)) {
+    // Check if the value already exists as a key in our new object
+    if (invertedObj[value] === undefined) {
+      // First time seeing this: Save it as a string
+      invertedObj[value] = key;
+    } else if (Array.isArray(invertedObj[value])) {
+      // It's already an array: Add the new key to the list
+      invertedObj[value].push(key);
+    } else {
+      // It's a string: Turn it into an array and add the new key
+      invertedObj[value] = [invertedObj[value], key];
+    }
+  }
 
-// e) Fix the implementation of invert (and write tests to prove it's fixed!)
+  return invertedObj;
+}
+
+// --- CONSOLE TESTS ---
+console.log("Test 1 (Simple):", invert({ a: 1 })); 
+// Expected: { "1": "a" }
+
+console.log("Test 2 (No duplicates):", invert({ x: 10, y: 20 })); 
+// Expected: { "10": "x", "20": "y" }
+
+console.log("Test 3 (Collision):", invert({ a: 1, b: 1 })); 
+// Expected: { "1": ["a", "b"] }
+
+console.log("Test 4 (Triple collision):", invert({ a: 1, b: 1, c: 1 })); 
+// Expected: { "1": ["a", "b", "c"] }

From 35a9a9b2286e2181e430c17ea46dc0baaa474d78 Mon Sep 17 00:00:00 2001
From: Mouawia Elkhalifa <moawia115@hotmail.com>
Date: Thu, 26 Mar 2026 22:22:52 +0000
Subject: [PATCH 2/4] fix: address mentor feedback for contains, tally, and
 invert

---
 Sprint-2/implement/contains.js      |  2 +-
 Sprint-2/implement/contains.test.js |  6 ++--
 Sprint-2/implement/querystring.js   |  8 +++--
 Sprint-2/implement/tally.js         | 11 ++----
 Sprint-2/implement/tally.test.js    | 27 ++++++++++++---
 Sprint-2/interpret/invert.js        | 54 ++++-------------------------
 Sprint-2/interpret/invert.test.js   | 33 ++++++++++++++++++
 7 files changed, 74 insertions(+), 67 deletions(-)
 create mode 100644 Sprint-2/interpret/invert.test.js

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index 81e8e7fab..3bc3fd5e2 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -3,7 +3,7 @@ function contains(obj, prop) {
     return false;
   }
 
-  return prop in obj;
+  return obj.hasOwn(obj, prop);
 }
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 26f1d8d4c..c0fe3fb76 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -41,6 +41,6 @@ test("return false when the property does not exist", () =>{
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
-test("return false when paramters invaliud ", () =>{
-    expect(contains([], "a")).toEqual(false)
-});
+test("returns false when input is an array", () => {
+  expect(contains([1, 2, 3], "0")).toEqual(false);
+});
\ No newline at end of file
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 7453d4cb3..cb1b233f1 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -11,11 +11,15 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
+    if (pair === "") continue;
+
     const [key, ...valueParts] = pair.split("=");
-    queryParams[key] = valueParts.join("=");
+    const value = valueParts.join("=");
+
+    queryParams[decodeURIComponent(key)] = decodeURIComponent(value);
   }
 
   return queryParams;
 }
 
-module.exports = parseQueryString;
+module.exports = parseQueryString;
\ No newline at end of file
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index 1f3b66638..3f649133b 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,17 +1,10 @@
 function tally(arr) {
-  //  invalid input → throw error
   if (!Array.isArray(arr)) {
     throw new Error("Input must be an array");
   }
 
-  //  empty array → return empty object
-  if (arr.length === 0) {
-    return {};
-  }
-
-  const result = {};
+  const result = Object.create(null);
 
-  //  count items
   for (const item of arr) {
     if (result[item] === undefined) {
       result[item] = 1;
@@ -23,4 +16,4 @@ function tally(arr) {
   return result;
 }
 
-module.exports = tally;
\ No newline at end of file
+module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 8632463f3..b39484b63 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -27,22 +27,39 @@ test("tally on an empty array returns an empty object", () => {
   expect(tally([])).toEqual({});
 });
 
-
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
 test("tally counts duplicate items correctly", () => {
-  expect(tally(['a', 'a', 'b', 'c'])).toEqual({
+  expect(tally(["a", "a", "b", "c"])).toEqual({
     a: 2,
     b: 1,
-    c: 1
+    c: 1,
   });
 });
 
-
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
 test("tally throws an error for invalid input", () => {
   expect(() => tally("hello")).toThrow();
-});
\ No newline at end of file
+});
+// Given an array containing keys that match built-in object properties
+// When passed to tally
+// Then it should correctly count them without conflicts from inherited properties
+test("tally works correctly with reserved words like toString", () => {
+  const input = ["toString", "toString", "hasOwnProperty"];
+  const expected = {
+    toString: 2,
+    hasOwnProperty: 1,
+  };
+  expect(tally(input)).toEqual(expected);
+});
+test("tally works correctly with reserved words like toString", () => {
+  const input = ["toString", "toString", "hasOwnProperty"];
+  const expected = {
+    toString: 2,
+    hasOwnProperty: 1,
+  };
+  expect(tally(input)).toEqual(expected);
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index 8fd6f05f0..b7229d3d7 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -1,38 +1,8 @@
-// Let's define how invert should work
-
-// Given an object
-// When invert is passed this object
-// Then it should swap the keys and values in the object
-
-// E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
-function invert(obj) {
-  const invertedObj = {};
-
-  for (const [key, value] of Object.entries(obj)) {
-    if (invertedObj[value] === undefined) {
-      invertedObj[value] = key;
-    } else if (Array.isArray(invertedObj[value])) {
-      invertedObj[value].push(key);
-    } else {
-      invertedObj[value] = [invertedObj[value], key];
-    }
-  }
-
-  return invertedObj;
-}
-// a) What is the current return value when invert is called with { a : 1 }
-//{"1": "a"}.
-// b) What is the current return value when invert is called with { a: 1, b: 2 }
-//{"1": "a", "2": "b"}
-// c) What is the target return value when invert is called with {a : 1, b: 2}
-//{"1": "a", "2": "b"}
-// c) What does Object.entries return? Why is it needed in this program?
-// Object.entries(obj) returns an array of [key, value] pairs, where each pair is stored as an array. 
-// It is needed in this program so we can loop through both the keys and values of the object at the same time when inverting it.
-//it returns an array of arrays, where each inner array is a pair: [key, value].
-//The current return value is different from the target output because when multiple keys have
-// the same value, they overwrite each other when inverted. This causes some values to be lost.
-// e) Fix the implementation of invert (and write tests to prove it's fixed!)
+/**
+ * Invert Function
+ * Swaps keys and values of an object. If multiple keys share the same value,
+ * it groups those keys into an array to prevent overwriting data.
+ */
 function invert(obj) {
   const invertedObj = {};
 
@@ -53,15 +23,5 @@ function invert(obj) {
   return invertedObj;
 }
 
-// --- CONSOLE TESTS ---
-console.log("Test 1 (Simple):", invert({ a: 1 })); 
-// Expected: { "1": "a" }
-
-console.log("Test 2 (No duplicates):", invert({ x: 10, y: 20 })); 
-// Expected: { "10": "x", "20": "y" }
-
-console.log("Test 3 (Collision):", invert({ a: 1, b: 1 })); 
-// Expected: { "1": ["a", "b"] }
-
-console.log("Test 4 (Triple collision):", invert({ a: 1, b: 1, c: 1 })); 
-// Expected: { "1": ["a", "b", "c"] }
+// Ensure this is at the bottom so other files can use it
+module.exports = invert;
\ No newline at end of file
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..2c7908744
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,33 @@
+const invert = require("./invert.js");
+
+/**
+ * invert function tests
+ * These tests verify that keys and values are swapped correctly.
+ * They also confirm that 'collisions' (where two keys share a value)
+ * result in an array of keys to prevent data loss.
+ */
+
+test("inverts a simple object", () => {
+  expect(invert({ a: 1 })).toEqual({ "1": "a" });
+});
+
+test("inverts object with different values", () => {
+  expect(invert({ x: 10, y: 20 })).toEqual({
+    "10": "x",
+    "20": "y",
+  });
+});
+
+test("handles duplicate values (Collision)", () => {
+  // Verifies that a single value found twice becomes an array
+  expect(invert({ a: 1, b: 1 })).toEqual({
+    "1": ["a", "b"],
+  });
+});
+
+test("handles multiple duplicate values (Triple Collision)", () => {
+  // Verifies that three keys sharing a value are all captured
+  expect(invert({ a: 1, b: 1, c: 1 })).toEqual({
+    "1": ["a", "b", "c"],
+  });
+});
\ No newline at end of file

From 9c4818e566bc2a5195a7a554e43ff272689e8a56 Mon Sep 17 00:00:00 2001
From: Mouawia Elkhalifa <moawia115@hotmail.com>
Date: Fri, 27 Mar 2026 08:29:19 +0000
Subject: [PATCH 3/4] Fix invert logic/comments and strengthen contains tests
 for Sprint 2

---
 Sprint-2/implement/contains.js      |  5 +++--
 Sprint-2/implement/contains.test.js | 21 ++++++++---------
 Sprint-2/implement/querystring.js   |  2 +-
 Sprint-2/implement/tally.test.js    | 10 +++++----
 Sprint-2/interpret/invert.js        | 35 ++++++++++++++++++++---------
 Sprint-2/interpret/invert.test.js   | 33 ---------------------------
 6 files changed, 46 insertions(+), 60 deletions(-)
 delete mode 100644 Sprint-2/interpret/invert.test.js

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index 3bc3fd5e2..40f559954 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -3,7 +3,8 @@ function contains(obj, prop) {
     return false;
   }
 
-  return obj.hasOwn(obj, prop);
+  // Use the static Object.hasOwn() method
+  return Object.hasOwn(obj, prop);
 }
 
-module.exports = contains;
+module.exports = contains;
\ No newline at end of file
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index c0fe3fb76..7d55a7581 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,27 +20,28 @@ as the object doesn't contains a key of 'c'
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test("contains on empty object returns false", () =>{
-    expect(contains({}, "a")).toEqual(false)
+test("contains on empty object returns false", () => {
+  expect(contains({}, "a")).toEqual(false);
 });
 
-
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
-test("contains an object with propery  exist, returns true", () =>{
-    expect(contains({a:1, b:2}, "a")).toEqual(true)
+test("contains an object with propery  exist, returns true", () => {
+  expect(contains({ a: 1, b: 2 }, "a")).toEqual(true);
 });
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
-test("return false when the property does not exist", () =>{
-    expect(contains({a:1, b:3}, "c")).toEqual(false)
+test("return false when the property does not exist", () => {
+  expect(contains({ a: 1, b: 3 }, "c")).toEqual(false);
 });
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
-test("returns false when input is an array", () => {
-  expect(contains([1, 2, 3], "0")).toEqual(false);
-});
\ No newline at end of file
+test("returns false when input is an array, even if the index exists", () => {
+  // Index 0 exists in this array, but contains() should return false 
+  // because the requirement is for plain objects only.
+  expect(contains(["apple", "banana"], 0)).toEqual(false);
+});
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index cb1b233f1..8a750be1f 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -22,4 +22,4 @@ function parseQueryString(queryString) {
   return queryParams;
 }
 
-module.exports = parseQueryString;
\ No newline at end of file
+module.exports = parseQueryString;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index b39484b63..0c19cd2b9 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -18,7 +18,7 @@ const tally = require("./tally.js");
 
 // Given a function called tally
 // When passed an array of items
-// Then it should return an object containing the count for each unique ite
+// Then it should return an object containing the count for each unique item
 
 // Given an empty array
 // When passed to tally
@@ -44,6 +44,7 @@ test("tally counts duplicate items correctly", () => {
 test("tally throws an error for invalid input", () => {
   expect(() => tally("hello")).toThrow();
 });
+
 // Given an array containing keys that match built-in object properties
 // When passed to tally
 // Then it should correctly count them without conflicts from inherited properties
@@ -55,11 +56,12 @@ test("tally works correctly with reserved words like toString", () => {
   };
   expect(tally(input)).toEqual(expected);
 });
-test("tally works correctly with reserved words like toString", () => {
-  const input = ["toString", "toString", "hasOwnProperty"];
+
+// Extra verification test to confirm pure object behavior
+test("tally accurately counts prototype method names as strings", () => {
+  const input = ["toString", "toString"];
   const expected = {
     toString: 2,
-    hasOwnProperty: 1,
   };
   expect(tally(input)).toEqual(expected);
 });
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index b7229d3d7..fdda515b2 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -1,21 +1,31 @@
-/**
- * Invert Function
- * Swaps keys and values of an object. If multiple keys share the same value,
- * it groups those keys into an array to prevent overwriting data.
- */
+// a) What is the current return value when invert is called with { a : 1 }
+// {"1": "a"}
+
+// b) What is the current return value when invert is called with { a: 1, b: 2 }
+// {"1": "a", "2": "b"}
+
+// c) What is the target return value when invert is called with {a : 1, b: 2}
+// {"1": "a", "2": "b"}
+
+// c) What does Object.entries return? Why is it needed in this program?
+// It returns an array of [key, value] pairs. It is needed to loop through both keys and values at the same time.
+
+// d) Explain why the current return value is different from the target output
+// The original code used 'invertedObj.key = value', which literally created a property named "key". 
+// It also didn't handle collisions, so values with the same key would overwrite each other.
+
+// e) Fix the implementation of invert (and write tests to prove it's fixed!)
 function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    // Check if the value already exists as a key in our new object
+    // We use [value] for dynamic keys. 
+    // We check if the key exists to handle collisions by creating an array.
     if (invertedObj[value] === undefined) {
-      // First time seeing this: Save it as a string
       invertedObj[value] = key;
     } else if (Array.isArray(invertedObj[value])) {
-      // It's already an array: Add the new key to the list
       invertedObj[value].push(key);
     } else {
-      // It's a string: Turn it into an array and add the new key
       invertedObj[value] = [invertedObj[value], key];
     }
   }
@@ -23,5 +33,10 @@ function invert(obj) {
   return invertedObj;
 }
 
-// Ensure this is at the bottom so other files can use it
+// --- CONSOLE TESTS TO PROVE IT IS FIXED ---
+console.log("Test 1 (Simple):", invert({ a: 1 })); 
+console.log("Test 2 (No duplicates):", invert({ x: 10, y: 20 })); 
+console.log("Test 3 (Collision):", invert({ a: 1, b: 1 })); 
+console.log("Test 4 (Triple collision):", invert({ a: 1, b: 1, c: 1 }));
+
 module.exports = invert;
\ No newline at end of file
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
deleted file mode 100644
index 2c7908744..000000000
--- a/Sprint-2/interpret/invert.test.js
+++ /dev/null
@@ -1,33 +0,0 @@
-const invert = require("./invert.js");
-
-/**
- * invert function tests
- * These tests verify that keys and values are swapped correctly.
- * They also confirm that 'collisions' (where two keys share a value)
- * result in an array of keys to prevent data loss.
- */
-
-test("inverts a simple object", () => {
-  expect(invert({ a: 1 })).toEqual({ "1": "a" });
-});
-
-test("inverts object with different values", () => {
-  expect(invert({ x: 10, y: 20 })).toEqual({
-    "10": "x",
-    "20": "y",
-  });
-});
-
-test("handles duplicate values (Collision)", () => {
-  // Verifies that a single value found twice becomes an array
-  expect(invert({ a: 1, b: 1 })).toEqual({
-    "1": ["a", "b"],
-  });
-});
-
-test("handles multiple duplicate values (Triple Collision)", () => {
-  // Verifies that three keys sharing a value are all captured
-  expect(invert({ a: 1, b: 1, c: 1 })).toEqual({
-    "1": ["a", "b", "c"],
-  });
-});
\ No newline at end of file

From 42a933ec5f4ac0e9b5e716d21f4a308cb7e2d91c Mon Sep 17 00:00:00 2001
From: Mouawia Elkhalifa <moawia115@hotmail.com>
Date: Fri, 27 Mar 2026 12:39:40 +0000
Subject: [PATCH 4/4] Final fix: Corrected invert answers (a-b) and
 strengthened contains tests

---
 Sprint-2/interpret/invert.js | 38 ++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index fdda515b2..88da66dd9 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -1,26 +1,27 @@
 // a) What is the current return value when invert is called with { a : 1 }
-// {"1": "a"}
+// { key: 1 }
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
-// {"1": "a", "2": "b"}
+// { key: 2 }
 
-// c) What is the target return value when invert is called with {a : 1, b: 2}
-// {"1": "a", "2": "b"}
+// c) What is the target return value when invert is called with { a: 1, b: 2 }
+// { "1": "a", "2": "b" }
 
-// c) What does Object.entries return? Why is it needed in this program?
-// It returns an array of [key, value] pairs. It is needed to loop through both keys and values at the same time.
+// d) What does Object.entries return? Why is it needed in this program?
+// It returns an array of [key, value] pairs.
+// It is needed so we can loop through both keys and values at the same time when inverting the object.
 
-// d) Explain why the current return value is different from the target output
-// The original code used 'invertedObj.key = value', which literally created a property named "key". 
-// It also didn't handle collisions, so values with the same key would overwrite each other.
+// e) Explain why the current return value is different from the target output
+// The original code used 'invertedObj.key = value', which creates a property literally named "key"
+// instead of using the value dynamically.
+// This causes each iteration to overwrite the previous one.
+// It also does not handle collisions (multiple keys with the same value).
 
-// e) Fix the implementation of invert (and write tests to prove it's fixed!)
+// f) Fix the implementation of invert (and write tests to prove it's fixed!)
 function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    // We use [value] for dynamic keys. 
-    // We check if the key exists to handle collisions by creating an array.
     if (invertedObj[value] === undefined) {
       invertedObj[value] = key;
     } else if (Array.isArray(invertedObj[value])) {
@@ -34,9 +35,16 @@ function invert(obj) {
 }
 
 // --- CONSOLE TESTS TO PROVE IT IS FIXED ---
-console.log("Test 1 (Simple):", invert({ a: 1 })); 
-console.log("Test 2 (No duplicates):", invert({ x: 10, y: 20 })); 
-console.log("Test 3 (Collision):", invert({ a: 1, b: 1 })); 
+console.log("Test 1 (Simple):", invert({ a: 1 }));
+// Expected: { '1': 'a' }
+
+console.log("Test 2 (No duplicates):", invert({ x: 10, y: 20 }));
+// Expected: { '10': 'x', '20': 'y' }
+
+console.log("Test 3 (Collision):", invert({ a: 1, b: 1 }));
+// Expected: { '1': ['a', 'b'] }
+
 console.log("Test 4 (Triple collision):", invert({ a: 1, b: 1, c: 1 }));
+// Expected: { '1': ['a', 'b', 'c'] }
 
 module.exports = invert;
\ No newline at end of file