diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..775abe36c 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,4 +1,6 @@
 // Predict and explain first...
+// The variable 'address' is an object, not an array,
+// so the code won't give the house number.
 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
@@ -12,4 +14,4 @@ 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..4b7bfc304 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,7 +1,10 @@
 // Predict and explain first...
+// - I predict that it won't work, because the variable 'value' isn't defined.
 
 // 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
+// - I was wrong, the error that it gives is that the variable 'author' is not iterable.
+// Checking for a solution...
 
 const author = {
   firstName: "Zadie",
@@ -11,6 +14,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+for (const key in author) {
+  console.log(author[key]);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..cf64108d8 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,8 +1,15 @@
 // Predict and explain first...
+// - The program will give the recipe title and serves,
+// but the ingredients will be undefined
+// because it calls the whole object at the end, instead of the key 'ingredients' of the object.
 
 // 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?
+// - First, I was wrong. The ingredients came out as 'object', not undefined.
+// - To fix it, I removed the object recipe from the first console.log,
+// and I used forEach to go through the 'recipe.ingredients' array and list all elements,
+// each on a new line.
 
 const recipe = {
   title: "bruschetta",
@@ -11,5 +18,8 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+  ingredients:`);
+
+recipe.ingredients.forEach((element) => {
+  console.log(element);
+});
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..d7fe7b128 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,22 @@
-function contains() {}
+function contains(object1, prop1) {
+  if (
+    typeof object1 !== "object" ||
+    object1 === null ||
+    Array.isArray(object1)
+  ) {
+    console.log("Error: object1 must be a non-null object and not an array.");
+    return false;
+  }
+
+  if (prop1 in object1) {
+    return true;
+  } else {
+    return false;
+  }
+}
+
+const myObject = [15, 20, 30];
+
+console.log(contains(myObject, "test2"));
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..3e65326ca 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,16 +20,59 @@ 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", () => {
+  const object = {};
+
+  expect(contains(object, "cat")).toBe(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("Given object with properties, should return true if the property name is in the object", () => {
+  const object1 = {
+    test1: 56,
+    test2: "cat",
+    test3: "dog",
+  };
+  expect(contains(object1, "test2")).toBe(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("When the property name isn't in the object, should return false", () => {
+  const object2 = {
+    test4: 52,
+    test5: "mango",
+    test6: "banana",
+  };
+  expect(contains(object2, "test7")).toBe(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("Given invalid parameters, should return false or an error", () => {
+  const array1 = ["duo", "mono", 105];
+
+  expect(contains(array1, "mono")).toBe(false);
+});
+
+//Given a string as an object
+//When passed to contains
+//Then it should return false
+test("Given a string as an object, should return false or an error", () => {
+  const string1 = "hello";
+
+  expect(contains(string1, "mono")).toBe(false);
+});
+
+//Given an object that's 'null'
+//When passed to contains
+//Then it should return false
+test("Given a null object, should return false or an error", () => {
+  const object3 = null;
+
+  expect(contains(object3, "mono")).toBe(false);
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..c5a5c6c2c 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,15 @@
-function createLookup() {
-  // implementation here
+function createLookup(nestedArray) {
+  let finalObject = {};
+
+  nestedArray.forEach((pair) => {
+    const key = pair[0];
+    const value = pair[1];
+    finalObject[key] = value;
+  });
+
+  return finalObject;
 }
 
+console.log(createLookup([["NG", "Naira"]]));
+
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..a41ed7fb9 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,12 @@
 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", () => {
+  testArray1 = [
+    ["US", "USD"],
+    ["DRC", "CDF"],
+  ];
+  expect(createLookup(testArray1)).toStrictEqual({ US: "USD", DRC: "CDF" });
+});
 
 /*
 
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..53399af0e 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -6,7 +6,8 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const [key, ...rest] = pair.split("=");
+    const value = rest.join("=");
     queryParams[key] = value;
   }
 
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..403c07f1e 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -3,10 +3,26 @@
 // 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");
 
 test("parses querystring values containing =", () => {
   expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
+    equation: "x=y+1",
   });
 });
+
+test("parses an empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("parses querystring with missing value", () => {
+  expect(parseQueryString("key=")).toEqual({ key: "" });
+});
+
+test("parses querystring with no equal sign", () => {
+  expect(parseQueryString("lonely")).toStrictEqual({ lonely: "" });
+});
+
+test("parses querystring with repeated values", () => {
+  expect(parseQueryString("a=1&a=2")).toEqual({ a: "2" });
+});
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..a2167e2a9 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,19 @@
-function tally() {}
+function tally(array) {
+  if (!Array.isArray(array)) {
+    throw new Error("Input must be an array");
+  }
+
+  const result = {};
+
+  for (const item of array) {
+    if (result[item]) {
+      result[item] = result[item] + 1;
+    } else {
+      result[item] = 1;
+    }
+  }
+
+  return result;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..5e33f6b49 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -23,12 +23,27 @@ 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", () => {
+  const testArray = [];
+
+  expect(tally(testArray)).toStrictEqual({});
+});
 
 // 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 duplicate items returns counts for each item", () => {
+  const testArray1 = ["a", "a", "b", "c"];
+
+  expect(tally(testArray1)).toStrictEqual({ 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 on an invalid input throws an error", () => {
+  const testArray2 = "mango";
+  const invalidInput = () => tally(testArray2);
+
+  expect(invalidInput).toThrow("Input must be an array");
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..c398b9aa0 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -10,20 +10,34 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
+const testObj = { a: 1, b: 2 };
+console.log(invert(testObj));
+
+module.exports = invert;
+
 // a) What is the current return value when invert is called with { a : 1 }
+// - The current return value is { key: 1 }
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// - The current return value is { key: 2 }
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// - The target return value is {"1": "a", "2": "b"}
 
 // c) What does Object.entries return? Why is it needed in this program?
+// - Object.entries returns an array of arrays,
+// where each inner array represents a [key, value] pair from the input object.
+// - It is needed to transform the given object into a nested array of the key-value pairs.
+// Then use that array to invert the object's key and value.
 
 // d) Explain why the current return value is different from the target output
+// - Because this line 13 creates a property named "key",
+// instead of inverting the original key and value.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..b2c44992f
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,21 @@
+const objectInvert = require("./invert.js");
+
+test("Inverting an object with one key and value", () => {
+  const test1 = { a: 1 };
+  expect(objectInvert(test1)).toEqual({ 1: "a" });
+});
+
+test("Inverting an object with two keys and values", () => {
+  const test2 = { a: 1, b: 2 };
+  expect(objectInvert(test2)).toEqual({ 1: "a", 2: "b" });
+});
+
+test("Inverting an empty object", () => {
+  const test3 = {};
+  expect(objectInvert(test3)).toEqual({});
+});
+
+test("Inverting an object with duplicate values", () => {
+  const test4 = { a: 1, b: 1, c: 2 };
+  expect(objectInvert(test4)).toEqual({ 1: "b", 2: "c" });
+});