From 5f153097509cc1d399190ea79860b33aa9abb2a3 Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Tue, 31 Mar 2026 15:26:18 +0100
Subject: [PATCH 01/15] predicting the output and debugging the code.

---
 Sprint-2/debug/address.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..f04f731c8 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// this code should log out undefined because even the object "address" is well defined but the property "houseNumber" is not being correctly accessed in the last line of code.
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -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}`);

From 5638fc490187647ca1b8bd6bae329c2c2e5ac3f6 Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Tue, 31 Mar 2026 15:41:25 +0100
Subject: [PATCH 02/15] predicting and debugging

---
 Sprint-2/debug/author.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..e9fa5b762 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// it should log out an error because the for statement is not correctly expressed and the prorties of the object are accessed instead of the values.
 // This program attempts to log out all the property values in the object.
 // But it isn't working. Explain why first and then fix the problem
 
@@ -11,6 +11,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+for (const value in author) {
+  console.log(author[value]);
 }

From 70fe1ba7d0bfddcc0c1f5a8118ea972ac26f088e Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Tue, 31 Mar 2026 15:49:39 +0100
Subject: [PATCH 03/15] predicting and debugging

---
 Sprint-2/debug/recipe.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..259f9a2ba 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// it should not log out the ingredients property's values because the ingredients are stored in an array and the code is not correctly accessing the array elements.
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
 // How can you fix it?
@@ -12,4 +12,4 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join("\n")}`);

From 648ae2883ecbb0f8768b955676ca3bc0711cccc9 Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Sun, 5 Apr 2026 16:31:07 +0100
Subject: [PATCH 04/15] implements a function that returns true if the object
 has a given property, and false otherwise

---
 Sprint-2/implement/contains.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..276ce3eab 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,6 @@
-function contains() {}
+function contains(obj, name) {
+  if (typeof obj == "object" || obj !== null || Object.keys(obj).length !== 0)
+    return Object.hasOwn(obj, name);
+}
 
 module.exports = contains;

From d76a207ed3f6f78b358b0542b79d48afb42b46bb Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Sun, 5 Apr 2026 17:15:30 +0100
Subject: [PATCH 05/15] implemented the createLookup function

---
 Sprint-2/implement/lookup.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..5c120898b 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,5 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  return Object.fromEntries(countryCurrencyPairs);
 }
 
 module.exports = createLookup;

From dcafc3b7a3694df9ce05b2a731db792ed4cc0702 Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Sun, 5 Apr 2026 19:18:33 +0100
Subject: [PATCH 06/15] cover missing case

---
 Sprint-2/implement/contains.js | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index 276ce3eab..03f3da11f 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,6 +1,7 @@
 function contains(obj, name) {
   if (typeof obj == "object" || obj !== null || Object.keys(obj).length !== 0)
     return Object.hasOwn(obj, name);
+  return false;
 }
 
 module.exports = contains;

From 2830956ba51d8003e6dd75342c24883ea90781ab Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Tue, 7 Apr 2026 15:58:43 +0100
Subject: [PATCH 07/15] completed the todo tests

---
 Sprint-2/implement/contains.test.js | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..c28f10082 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,16 +20,31 @@ 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("given an empty object, returns false", () => {
+  expect(contains({}, "x")).toEqual(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("given an object with properties, returns true when passed to contains with an existing property name", () => {
+  expect(
+    contains({ gitName: "djebsoft", position: "cyf trainee" }, "gitName")
+  ).toEqual(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("given an object with properties, returns false when passed to contains with a non-existent property name", () => {
+  expect(
+    contains({ gitName: "djebsoft", position: "cyf trainee" }, "age")
+  ).toEqual(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("given invalid parameters, returns false or throws an error", () => {
+  expect(contains(["gitName", "position"], "gitName")).toEqual(false);
+});

From 611d2471a0bec575b133396c0c2fcd9952f168b4 Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Thu, 9 Apr 2026 00:10:38 +0100
Subject: [PATCH 08/15] complted sprint-2 coursework

---
 Sprint-2/implement/lookup.js           | 25 +++++++-
 Sprint-2/implement/lookup.test.js      | 44 +++++++++++++-
 Sprint-2/implement/querystring.js      | 11 +++-
 Sprint-2/implement/querystring.test.js | 79 +++++++++++++++++++++++++-
 Sprint-2/implement/tally.js            | 13 ++++-
 Sprint-2/implement/tally.test.js       | 53 ++++++++++++++++-
 Sprint-2/interpret/invert.js           | 14 ++++-
 Sprint-2/interpret/invert.test.js      | 36 ++++++++++++
 8 files changed, 260 insertions(+), 15 deletions(-)
 create mode 100644 Sprint-2/interpret/invert.test.js

diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index 5c120898b..8de5ff2db 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,24 @@
-function createLookup(countryCurrencyPairs) {
-  return Object.fromEntries(countryCurrencyPairs);
+// the first element is the country code
+// the second array is the currency code of the country
+// the function should return an object
+// the keys of the object should be the first element of each inner array (country code)
+// the values of the object should be the second element of each inner array (currency code)
+
+function Lookup(coCuPairs) {
+  // check if the argument is an array of arrays
+  if (
+    Array.isArray(coCuPairs) &&
+    // check if each inner array is an array.
+    coCuPairs.every((pair) => Array.isArray(pair)) &&
+    // check if each inner array has two elements.
+    coCuPairs.every((pair) => pair.length === 2)
+    // we can also use index to check the pair is an array as follows:
+    // for (let i = 0; i < coCuPairs.length; i++)
+    //  return Array.isArray(coCuPairs[i])
+  ) {
+    return Object.fromEntries(coCuPairs);
+  }
+  return "Invalid input: expected an array of arrays";
 }
 
-module.exports = createLookup;
+module.exports = Lookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..e7ad82a83 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,18 @@
-const createLookup = require("./lookup.js");
+const Lookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+test("creates a country currency code lookup for multiple codes", () => {
+  const input = [
+    ["DZ", "DZD"],
+    ["CA", "CAD"],
+    ["GB", "GBP"],
+  ];
+  const result = {
+    DZ: "DZD",
+    CA: "CAD",
+    GB: "GBP",
+  };
+  expect(Lookup(input)).toEqual(result);
+});
 
 /*
 
@@ -24,7 +36,7 @@ Example
 Given: [['US', 'USD'], ['CA', 'CAD']]
 
 When
-createLookup(countryCurrencyPairs) is called
+Lookup(coCuPairs) is called
 
 Then
 It should return:
@@ -33,3 +45,29 @@ It should return:
    'CA': 'CAD'
  }
 */
+// Given an invalid input (not an array of arrays),
+test('return "Invalid input: expected an array of arrays" for string input', () => {
+  const input = "invalid input: expected an array of arrays";
+  expect(Lookup(input)).toEqual("Invalid input: expected an array of arrays");
+});
+
+// Given an array where its elements are not arrays,
+test('return "Invalid input: expected an array of arrays" for non-array elements', () => {
+  const input = [["US", "USD"], "CA"];
+  expect(Lookup(input)).toEqual("Invalid input: expected an array of arrays");
+});
+
+// Given an array where its elements are arrays with more than two elements,
+test('return "Invalid input: expected an array of arrays" for arrays with too many elements', () => {
+  const input = [
+    ["US", "USD", "flag"],
+    ["CA", "CAD"],
+  ];
+  expect(Lookup(input)).toEqual("Invalid input: expected an array of arrays");
+});
+
+// Given an array where its elements are arrays with less than two elements,
+test('return "Invalid input: expected an array of arrays" for arrays with too few elements', () => {
+  const input = [["US", "USD"], ["CA"]];
+  expect(Lookup(input)).toEqual("Invalid input: expected an array of arrays");
+});
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..cad8592a6 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,13 +1,20 @@
+// the bug in the code is that it does not handle cases where the query string has two = signs or more between two parameters.
+// in this case we make sure to split the string only at the first = sign.
+// so we use the spread operator.
 function parseQueryString(queryString) {
   const queryParams = {};
+  if (queryString === null || queryString === undefined) {
+    return "invalid query string";
+  }
   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, ...value] = pair.split("=");
+    // we convert the value array back to a string and we get back the = signs by using it as separator.
+    queryParams[key] = value.join("=");
   }
 
   return queryParams;
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..d9171b8c9 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -3,10 +3,85 @@
 // Below is one test case for an edge case the implementation doesn't handle well.
 // Fix the implementation for this test, and try to think of as many other edge cases as possible - write tests and fix those too.
 
-const parseQueryString = require("./querystring.js")
+const parseQueryString = require("./querystring.js");
 
+// testing when the query string with a value contains = signs
 test("parses querystring values containing =", () => {
   expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
+    equation: "x=y+1",
+  });
+});
+
+// testing when the query string has multiple ampersands
+test("parses query string with multiple parameters", () => {
+  expect(parseQueryString("name=Ben&age=45&city=new%20city")).toEqual({
+    name: "Ben",
+    age: "45",
+    city: "new%20city",
+  });
+});
+
+// testing when the query string has two ampersands in a row
+test("parses query string with two ampersands in a row", () => {
+  expect(parseQueryString("name=Ben&&age=45")).toEqual({
+    name: "Ben",
+    "": "",
+    age: "45",
+  });
+});
+
+// testing when the query string has no ampersands
+test("parses query string with no ampersands", () => {
+  expect(parseQueryString("name=Ben")).toEqual({
+    name: "Ben",
+  });
+});
+
+// testing when the query string has no ampersands and no equal signs
+test("parses query string with no ampersands and no equal signs", () => {
+  expect(parseQueryString("name")).toEqual({
+    name: "",
+  });
+});
+
+// testing when the query string is empty
+test("parses query string with empty value", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+// testing when the query string is null
+test("parses query string with null value", () => {
+  expect(parseQueryString(null)).toEqual("invalid query string");
+});
+
+// testing when the query string is undefined
+test("parses query string with undefined value", () => {
+  expect(parseQueryString(undefined)).toEqual("invalid query string");
+});
+
+// testing when a pair ends with equal sign (no value)
+test("parses query string with no equal sign", () => {
+  expect(parseQueryString("name=Ben&age=&city=")).toEqual({
+    name: "Ben",
+    age: "",
+    city: "",
+  });
+});
+
+// testing when a pair starts with equal sign (no key)
+test("parses query string starting with equal sign", () => {
+  expect(parseQueryString("name=Ben&=45")).toEqual({
+    name: "Ben",
+    "": "45",
+  });
+});
+
+// testing when a pair has no equal sign (no value and no key)
+// the pair will be the key and the value will be an empty string
+test("parses query string with no equal sign", () => {
+  expect(parseQueryString("name&age=45&city")).toEqual({
+    name: "",
+    age: "45",
+    city: "",
   });
 });
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..955f2c482 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,12 @@
-function tally() {}
-
+function tally(arr) {
+  if (!Array.isArray(arr)) {
+    throw new Error("invalid input");
+  }
+  let result = {};
+  for (let i = 0; i <= arr.length - 1; i++) {
+    let item = arr[i];
+    result[item] = (result[item] || 0) + 1;
+  }
+  return result;
+}
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..3dd61e91e 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -23,12 +23,63 @@ const tally = require("./tally.js");
 // 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 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 on an array with duplicates returns correct counts for each unique item", () => {
+  expect(
+    tally([
+      "CYF",
+      "CYF",
+      "AWS",
+      "Capgemini",
+      "Deloitte",
+      "Google",
+      "Slack",
+      "Capgemini",
+    ])
+  ).toEqual({ CYF: 2, AWS: 1, Capgemini: 2, Deloitte: 1, Google: 1, Slack: 1 });
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("given invalid input throws an error", () => {
+  expect(() => tally("invalid")).toThrow("invalid input");
+});
+
+// Given an invalid input like a number
+test("given invalid input throws an error", () => {
+  expect(() => tally("invalid")).toThrow("invalid input");
+});
+
+// Given an invalid input like a number
+test("given invalid input throws an error", () => {
+  expect(() => tally(123)).toThrow("invalid input");
+});
+
+// Given an invalid input like an object
+test("given invalid input throws an error", () => {
+  expect(() => tally({})).toThrow("invalid input");
+});
+
+// Given an invalid input like null
+test("given invalid input throws an error", () => {
+  expect(() => tally(null)).toThrow("invalid input");
+});
+
+// Given an invalid input like undefined
+test("given invalid input throws an error", () => {
+  expect(() => tally(undefined)).toThrow("invalid input");
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..e8bd4fb20 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -8,22 +8,32 @@
 
 function invert(obj) {
   const invertedObj = {};
-
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj))
+    return invertedObj;
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
 // a) What is the current return value when invert is called with { a : 1 }
+// {key: 1}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// {key: 2}
 
 // 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 the pairs properties [key, value] of the object.
+// it is needed in this program to iterate over the key value pairs of the object to swap them in new object.
 
 // d) Explain why the current return value is different from the target output
+// because first it doesn't swap.
+// second, we're using the dot notation to assign the value where we should user the brackets notation as the key is variable and not a string literal.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+module.exports = invert;
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..927bed307
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,36 @@
+const invert = require("./invert.js");
+// writing some tests.
+// Given an simple ordinary object.
+test("invert on a simple object returns the correct inverted object", () => {
+  expect(invert({ a: 1 })).toEqual({ 1: "a" });
+});
+// Given an object with multiple key value pairs.
+test("invert on an object with multiple key value pairs returns the correct inverted object", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ 1: "a", 2: "b" });
+});
+// Given an object with duplicate values.
+test("invert on an object with duplicate values returns the correct inverted object", () => {
+  expect(invert({ a: 1, b: 1 })).toEqual({ 1: "a", 1: "b" });
+});
+// Given an empty object.
+test("invert on an empty object returns an empty object", () => {
+  expect(invert({})).toEqual({});
+});
+// Given an invalid input like a string.
+test("invert on an invalid input like a string returns an empty object", () => {
+  expect(invert("invalid")).toEqual({});
+});
+
+// Given an invalid input like a number.
+test("invert on an invalid input like a number returns an empty object", () => {
+  expect(invert(123)).toEqual({});
+});
+// Given an invalid input like an array.
+test("invert on an invalid input like an array returns an empty object", () => {
+  expect(invert([1, 2, 3])).toEqual({});
+});
+// Given an invalid input like null or undefined.
+test("invert on an invalid input like null or undefined returns an empty object", () => {
+  expect(invert(null)).toEqual({});
+  expect(invert(undefined)).toEqual({});
+});

From 0dddbf3170215d217bcfc3a6f791ff78e06772ae Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Thu, 9 Apr 2026 08:52:33 +0100
Subject: [PATCH 09/15] fixed contains function

---
 Sprint-2/implement/contains.js      | 7 ++++---
 Sprint-2/implement/contains.test.js | 6 +++++-
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index 03f3da11f..a49b5cf01 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,7 +1,8 @@
 function contains(obj, name) {
-  if (typeof obj == "object" || obj !== null || Object.keys(obj).length !== 0)
-    return Object.hasOwn(obj, name);
-  return false;
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    return false;
+  }
+  return Object.hasOwn(obj, name);
 }
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index c28f10082..7c326b099 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -45,6 +45,10 @@ test("given an object with properties, returns false when passed to contains wit
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
-test("given invalid parameters, returns false or throws an error", () => {
+test("given invalid parameters (array), returns false or throws an error", () => {
   expect(contains(["gitName", "position"], "gitName")).toEqual(false);
 });
+
+test("given invalid parameters (like null or undefined), returns false or throws an error", () => {
+  expect(contains(null, "gitName")).toEqual(false);
+});

From e90345044ea20d7c2e6f6af3650c2aeb853296aa Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Thu, 9 Apr 2026 09:08:31 +0100
Subject: [PATCH 10/15] changed the name of the parameter

---
 Sprint-2/implement/lookup.js      | 14 +++++++-------
 Sprint-2/implement/lookup.test.js |  2 +-
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index 8de5ff2db..0a2c058da 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -4,19 +4,19 @@
 // the keys of the object should be the first element of each inner array (country code)
 // the values of the object should be the second element of each inner array (currency code)
 
-function Lookup(coCuPairs) {
+function Lookup(countryCurrencyPairs) {
   // check if the argument is an array of arrays
   if (
-    Array.isArray(coCuPairs) &&
+    Array.isArray(countryCurrencyPairs) &&
     // check if each inner array is an array.
-    coCuPairs.every((pair) => Array.isArray(pair)) &&
+    countryCurrencyPairs.every((pair) => Array.isArray(pair)) &&
     // check if each inner array has two elements.
-    coCuPairs.every((pair) => pair.length === 2)
+    countryCurrencyPairs.every((pair) => pair.length === 2)
     // we can also use index to check the pair is an array as follows:
-    // for (let i = 0; i < coCuPairs.length; i++)
-    //  return Array.isArray(coCuPairs[i])
+    // for (let i = 0; i < countryCurrencyPairs.length; i++)
+    //  return Array.isArray(countryCurrencyPairs[i])
   ) {
-    return Object.fromEntries(coCuPairs);
+    return Object.fromEntries(countryCurrencyPairs);
   }
   return "Invalid input: expected an array of arrays";
 }
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index e7ad82a83..23b6703e1 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -36,7 +36,7 @@ Example
 Given: [['US', 'USD'], ['CA', 'CAD']]
 
 When
-Lookup(coCuPairs) is called
+Lookup(countryCurrencyPairs) is called
 
 Then
 It should return:

From 5eee074fd594c4eafbfd50677e33b7a437ddd8ba Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Thu, 9 Apr 2026 09:51:29 +0100
Subject: [PATCH 11/15] throw an error instead

---
 Sprint-2/implement/lookup.js | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index 0a2c058da..9598f2dfe 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -7,18 +7,18 @@
 function Lookup(countryCurrencyPairs) {
   // check if the argument is an array of arrays
   if (
-    Array.isArray(countryCurrencyPairs) &&
+    !Array.isArray(countryCurrencyPairs) ||
     // check if each inner array is an array.
-    countryCurrencyPairs.every((pair) => Array.isArray(pair)) &&
+    !countryCurrencyPairs.every((pair) => Array.isArray(pair)) ||
     // check if each inner array has two elements.
-    countryCurrencyPairs.every((pair) => pair.length === 2)
+    !countryCurrencyPairs.every((pair) => pair.length === 2)
     // we can also use index to check the pair is an array as follows:
     // for (let i = 0; i < countryCurrencyPairs.length; i++)
     //  return Array.isArray(countryCurrencyPairs[i])
   ) {
-    return Object.fromEntries(countryCurrencyPairs);
+    throw new Error("Invalid input: expected an array of arrays");
   }
-  return "Invalid input: expected an array of arrays";
+  return Object.fromEntries(countryCurrencyPairs);
 }
 
 module.exports = Lookup;

From df82c4f706302b54e029ca8e36c7178ff29f49c1 Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Thu, 9 Apr 2026 13:06:23 +0100
Subject: [PATCH 12/15] fixed all errors to pass all tests

---
 Sprint-2/implement/lookup.js      |  4 ++--
 Sprint-2/implement/lookup.test.js | 28 ++++++++++++++++++----------
 Sprint-2/implement/tally.js       |  3 ++-
 Sprint-2/implement/tally.test.js  | 21 +++++++++------------
 4 files changed, 31 insertions(+), 25 deletions(-)

diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index 9598f2dfe..944eb404c 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -9,9 +9,9 @@ function Lookup(countryCurrencyPairs) {
   if (
     !Array.isArray(countryCurrencyPairs) ||
     // check if each inner array is an array.
-    !countryCurrencyPairs.every((pair) => Array.isArray(pair)) ||
+    countryCurrencyPairs.some((pair) => !Array.isArray(pair)) ||
     // check if each inner array has two elements.
-    !countryCurrencyPairs.every((pair) => pair.length === 2)
+    countryCurrencyPairs.some((pair) => pair.length !== 2)
     // we can also use index to check the pair is an array as follows:
     // for (let i = 0; i < countryCurrencyPairs.length; i++)
     //  return Array.isArray(countryCurrencyPairs[i])
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 23b6703e1..1909a7039 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -46,28 +46,36 @@ It should return:
  }
 */
 // Given an invalid input (not an array of arrays),
-test('return "Invalid input: expected an array of arrays" for string input', () => {
-  const input = "invalid input: expected an array of arrays";
-  expect(Lookup(input)).toEqual("Invalid input: expected an array of arrays");
+test('given string input throw "Invalid input: expected an array of arrays"', () => {
+  let input = "invalid input: expected an array of arrays";
+  expect(() => Lookup(input)).toThrow(
+    "Invalid input: expected an array of arrays"
+  );
 });
 
 // Given an array where its elements are not arrays,
-test('return "Invalid input: expected an array of arrays" for non-array elements', () => {
-  const input = [["US", "USD"], "CA"];
-  expect(Lookup(input)).toEqual("Invalid input: expected an array of arrays");
+test('given array with non-array elements throw "Invalid input: expected an array of arrays"', () => {
+  let input = [["US", "USD"], "CA"];
+  expect(() => Lookup(input)).toThrow(
+    "Invalid input: expected an array of arrays"
+  );
 });
 
 // Given an array where its elements are arrays with more than two elements,
-test('return "Invalid input: expected an array of arrays" for arrays with too many elements', () => {
+test('given arrays with too many elements throw "Invalid input: expected an array of arrays"', () => {
   const input = [
     ["US", "USD", "flag"],
     ["CA", "CAD"],
   ];
-  expect(Lookup(input)).toEqual("Invalid input: expected an array of arrays");
+  expect(() => Lookup(input)).toThrow(
+    "Invalid input: expected an array of arrays"
+  );
 });
 
 // Given an array where its elements are arrays with less than two elements,
-test('return "Invalid input: expected an array of arrays" for arrays with too few elements', () => {
+test('given arrays with too few elements throw "Invalid input: expected an array of arrays"', () => {
   const input = [["US", "USD"], ["CA"]];
-  expect(Lookup(input)).toEqual("Invalid input: expected an array of arrays");
+  expect(() => Lookup(input)).toThrow(
+    "Invalid input: expected an array of arrays"
+  );
 });
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index 955f2c482..ab2ba96bc 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -2,7 +2,8 @@ function tally(arr) {
   if (!Array.isArray(arr)) {
     throw new Error("invalid input");
   }
-  let result = {};
+  // using Object.create(null) to create a plain object without prototype
+  let result = Object.create(null);
   for (let i = 0; i <= arr.length - 1; i++) {
     let item = arr[i];
     result[item] = (result[item] || 0) + 1;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 3dd61e91e..68e1ec667 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -27,13 +27,6 @@ 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 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
@@ -52,6 +45,15 @@ test("tally on an array with duplicates returns correct counts for each unique i
   ).toEqual({ CYF: 2, AWS: 1, Capgemini: 2, Deloitte: 1, Google: 1, Slack: 1 });
 });
 
+test("tally on an array with duplicates returns correct counts for each unique item", () => {
+  expect(tally(["toString", "toString"])).toEqual({ toString: 2 });
+});
+
+// Given an input that you mentioned in the review.
+//test("tally on an array with duplicates returns correct counts for each unique item", () => {
+//  expect(tally(["toString", "toString"])).toEqual({ toString: 2 });
+//});
+
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
@@ -59,11 +61,6 @@ test("given invalid input throws an error", () => {
   expect(() => tally("invalid")).toThrow("invalid input");
 });
 
-// Given an invalid input like a number
-test("given invalid input throws an error", () => {
-  expect(() => tally("invalid")).toThrow("invalid input");
-});
-
 // Given an invalid input like a number
 test("given invalid input throws an error", () => {
   expect(() => tally(123)).toThrow("invalid input");

From 6a6d255c5794d3ac3f488f77a1e01199d7ea5d5a Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Thu, 9 Apr 2026 13:28:52 +0100
Subject: [PATCH 13/15] adjusted the function name

---
 Sprint-2/implement/lookup.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index 944eb404c..a5bb64409 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -4,7 +4,7 @@
 // the keys of the object should be the first element of each inner array (country code)
 // the values of the object should be the second element of each inner array (currency code)
 
-function Lookup(countryCurrencyPairs) {
+function createLookup(countryCurrencyPairs) {
   // check if the argument is an array of arrays
   if (
     !Array.isArray(countryCurrencyPairs) ||
@@ -21,4 +21,4 @@ function Lookup(countryCurrencyPairs) {
   return Object.fromEntries(countryCurrencyPairs);
 }
 
-module.exports = Lookup;
+module.exports = createLookup;

From 57fab6119bb25fc5b018e3791ca69b16738f6b07 Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Thu, 9 Apr 2026 17:41:18 +0100
Subject: [PATCH 14/15] updated the array input test.

---
 Sprint-2/implement/contains.test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 7c326b099..1548d3e8d 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -46,7 +46,7 @@ test("given an object with properties, returns false when passed to contains wit
 // When passed to contains
 // Then it should return false or throw an error
 test("given invalid parameters (array), returns false or throws an error", () => {
-  expect(contains(["gitName", "position"], "gitName")).toEqual(false);
+  expect(contains(["gitName", "age", "position"], "cohort")).toEqual(false);
 });
 
 test("given invalid parameters (like null or undefined), returns false or throws an error", () => {

From 5f437296a46a9fd69f86f943d0924fcbb033e576 Mon Sep 17 00:00:00 2001
From: boladjebsoft <djebbour1985@gmail.com>
Date: Thu, 9 Apr 2026 19:34:15 +0100
Subject: [PATCH 15/15] udated the array input test

---
 Sprint-2/implement/contains.test.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 1548d3e8d..9acbfd464 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -45,8 +45,9 @@ test("given an object with properties, returns false when passed to contains wit
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+// "length" is perfect for the test because it's real property on the array itself
 test("given invalid parameters (array), returns false or throws an error", () => {
-  expect(contains(["gitName", "age", "position"], "cohort")).toEqual(false);
+  expect(contains(["gitName", "age", "position"], "length")).toBe(false);
 });
 
 test("given invalid parameters (like null or undefined), returns false or throws an error", () => {