diff --git a/.gitignore b/.gitignore
index bde36e530..bc563efa0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 node_modules
 .DS_Store
 .vscode
-**/.DS_Store
\ No newline at end of file
+**/.DS_Store
+prep
\ No newline at end of file
diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..eba953a5d 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,5 +1,7 @@
 // Predict and explain first...
-
+/*
+My prediction why code isn't working is that we can't access properties in object using index. We need to call the by key value
+*/
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that 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..4a32e31ff 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,5 +1,7 @@
 // Predict and explain first...
-
+/*
+I think the problem is because we try access property in object without saying what exactly property we need
+*/
 // 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 +13,6 @@ 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..52cbcd365 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,5 +1,7 @@
 // Predict and explain first...
-
+/*
+I think we need to use iteration to access and log ingredients one by one
+*/
 // 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?
@@ -11,5 +13,7 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+  ingredients:`);
+for (let ingredientIndex in recipe.ingredients) {
+  console.log(recipe.ingredients[ingredientIndex]);
+}
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..caa4e1d21 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,5 @@
-function contains() {}
+function contains(object, property) {
+  return Object.keys(object).includes(property);
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..5b9542728 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -16,20 +16,31 @@ as the object doesn't contains a key of 'c'
 // Given a contains function
 // When passed an object and a property name
 // Then it should return true if the object contains the property, false otherwise
-
-// Given an empty object
-// When passed to contains
-// Then it should return false
-test.todo("contains on empty object returns false");
-
-// Given an object with properties
-// When passed to contains with an existing property name
-// Then it should return true
-
-// Given an object with properties
-// When passed to contains with a non-existent property name
-// Then it should return false
-
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error
+describe("contains", () => {
+  // Given an empty object
+  // When passed to contains
+  // Then it should return false
+  test("Given an empty object, return false", () => {
+    expect(contains({})).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, when passed an existing property name, return 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("Given an object with properties, when passed a non-existent property name, return false", () => {
+    expect(contains({ a: 1, b: 2 }, "c")).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 like an array, return false or throw an error", () => {
+    expect(contains(["a", 1, "b", 2, "c"])).toEqual(false);
+  });
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..e6d9e71a0 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,9 @@
-function createLookup() {
-  // implementation here
-}
+function createLookup(array) {
+  const countryCurrencyObject = {};
+  for (const index in array) {
+    countryCurrencyObject[array[index][0]] = array[index][1]
+  };
+  return countryCurrencyObject
+};
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..c8c0bc247 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,35 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+describe("function is called with the country-currency array as an argument", () => {
+  test("It should return an object", () => {
+    expect(
+      typeof createLookup([
+        ["US", "USD"],
+        ["CA", "CAD"],
+      ])
+    ).toEqual("object");
+  });
+  test("The keys are the country codes", () => {
+    expect(
+      Object.keys(
+        createLookup([
+          ["US", "USD"],
+          ["CA", "CAD"],
+        ])
+      )
+    ).toEqual(["US", "CA"]);
+  });
+  test("The values are the corresponding currency codes", () => {
+    expect(
+      Object.values(
+        createLookup([
+          ["US", "USD"],
+          ["CA", "CAD"],
+        ])
+      )
+    ).toEqual(["USD", "CAD"]);
+  });
+});
 
 /*
 
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..f4eed9b1a 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -6,7 +6,9 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const decodedPair = decodeURIComponent(pair);
+    const [key, value] = decodedPair.split(/=(.*)/s);
+
     queryParams[key] = value;
   }
 
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..f99d362ba 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -3,10 +3,16 @@
 // 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",
   });
 });
+
+test("parses querystring encoded values containing =", () => {
+  expect(parseQueryString("a%25b=c%26d")).toEqual({
+    "a%b": "c&d",
+  });
+});
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..775506afa 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,11 @@
-function tally() {}
+function tally(arrayOfItems) {
+  object = {};
+  if (!Array.isArray(arrayOfItems)) {
+    throw new Error("Invalid input");
+  } else {
+    for (char of arrayOfItems) object[char] = (object[char] || 0) + 1;
+    return object;
+  }
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..509fc168b 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -19,16 +19,26 @@ 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
+describe("Given a function called tally, return an object containing the count for each unique item", () => {
+  // Given an empty array
+  // When passed to tally
+  // Then it should return an empty object
+  test("tally on an empty array returns an empty object", () => {
+    expect(tally([])).toEqual({});
+  });
 
-// 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");
+  // Given an array with duplicate items
+  // When passed to tally
+  // Then it should return counts for each unique item
+  test("Given an array with duplicate items, return counts for each unique item", () => {
+      expect(tally(["a", "a", "a"])).toEqual({ a: 3 });
+      expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 1 });
+  });
 
-// Given an array with duplicate items
-// When passed to tally
-// Then it should return counts for each unique item
-
-// Given an invalid input like a string
-// When passed to tally
-// Then it should throw an error
+  // Given an invalid input like a string
+  // When passed to tally
+  // Then it should throw an error
+  test("Given an invalid input like a string, throw an error", () => {
+    expect(() => tally("a,a,b,c")).toThrow("Invalid input");
+  });
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..a0df5479a 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -6,24 +6,45 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
-function invert(obj) {
-  const invertedObj = {};
+// function invert(obj) {
+//   const invertedObj = {};
 
-  for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
-  }
-
-  return invertedObj;
-}
+//   for (const [key, value] of Object.entries(obj)) {
+//     invertedObj.key = value;
+//   }
 
+//   return invertedObj;
+// }
+// console.log(invert({ a: 1, b: 2 }));
 // 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 string-keyed key-value pairs from the given object
 
 // d) Explain why the current return value is different from the target output
 
+// We want to add a property name to the object that is the value of the key variable and not the string "key".
+// We can do this with square bracket notation
+
+// current code creates an object property, where key is key and value is value.
+// But we need to swap the key and value.
+
 // 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)) {
+    invertedObj[value] = key;
+  }
+
+  return invertedObj;
+}
+
+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..a1bec199a
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,8 @@
+const invert = require("./invert.js");
+
+describe("proof function is fixed", () => {
+  test("Given an object, it should swap the keys and values in the object", () => {
+    expect(invert({ x: 10, y: 20 })).toEqual({ 10: "x", 20: "y" });
+    expect(invert({ a: 1, b: 2 })).toEqual({ 1: "a", 2: "b" });
+  });
+});