diff --git a/sprint-3-stretch-exercises/credit-card-validator.js b/sprint-3-stretch-exercises/credit-card-validator.js
new file mode 100644
index 000000000..73414a95d
--- /dev/null
+++ b/sprint-3-stretch-exercises/credit-card-validator.js
@@ -0,0 +1,32 @@
+export function creditCardValidator(cardNumber) {
+  // rejects the number if itn's exactly 16 characters
+  if (cardNumber.length !== 16) {
+    return false;
+  }
+  // the last digit must be even, so reject it if dividing by 2 leaves a reminder
+  if (cardNumber.slice(-1) % 2 !== 0) {
+    return false;
+  }
+
+  let hasDifferentDigit = false;
+  let digitSum = 0;
+
+  for (const digit of cardNumber) {
+    // every character must be a digit from 0 to 9
+    if (digit < "0" || digit > "9") {
+      return false;
+    }
+    digitSum += Number(digit);
+
+    // if any digit differs from the first one, at least two different digits are used
+    if (digit !== cardNumber[0]) {
+      hasDifferentDigit = true;
+    }
+  }
+
+  // needs two different digits and a digit sum greater than 16
+  if (!hasDifferentDigit || digitSum <= 16) {
+    return false;
+  }
+  return true;
+}
diff --git a/sprint-3-stretch-exercises/credit-card-validator.test.js b/sprint-3-stretch-exercises/credit-card-validator.test.js
new file mode 100644
index 000000000..ac851aa61
--- /dev/null
+++ b/sprint-3-stretch-exercises/credit-card-validator.test.js
@@ -0,0 +1,42 @@
+// Case 1 valid card numbers.
+import { creditCardValidator } from "./credit-card-validator.js";
+test("should return true for a valid card number", () => {
+  const number = "2222222222222224";
+  const result = creditCardValidator(number);
+  expect(result).toEqual(true);
+});
+
+// Case 2 number must be 16 digits.
+test("should return false when the numbers has fewer than 16 digits", () => {
+  const number = "123";
+  const result = creditCardValidator(number);
+  expect(result).toEqual(false);
+});
+
+// Case 3 numbers must be whole numbers.
+test("should return false when the number contains a letter", () => {
+  const number = "22222222222222b4";
+  const result = creditCardValidator(number);
+  expect(result).toEqual(false);
+});
+
+// Case 4 numbers must have at least two different digits represented.
+test("should return false when all digits are the same.", () => {
+  const number = "2222222222222222";
+  const result = creditCardValidator(number);
+  expect(result).toEqual(false);
+});
+
+// Case 5 the final digit of the number must be even.
+test("should return false when the last digit is odd", () => {
+  const number = "2222222222222223";
+  const result = creditCardValidator(number);
+  expect(result).toEqual(false);
+});
+
+// Case 6 the sum of all the digits must be greater than 16.
+test("should return false when the sum of digits is 16 or less", () => {
+  const number = "1111111111110002";
+  const result = creditCardValidator(number);
+  expect(result).toEqual(false);
+});
diff --git a/sprint-3-stretch-exercises/find.js b/sprint-3-stretch-exercises/find.js
index c7e79a2f2..e4c61c3f1 100644
--- a/sprint-3-stretch-exercises/find.js
+++ b/sprint-3-stretch-exercises/find.js
@@ -20,6 +20,10 @@ console.log(find("code your future", "z"));
 // Pay particular attention to the following:
 
 // a) How the index variable updates during the call to find
+// -   index starts at 0 and increase by 1 each time in the loop. When a character match is found the index return and the function stops.
 // b) What is the if statement used to check
+// -   It checks whether the character at position index of str is exactly equal to char. If so it returns that position.
 // c) Why is index++ being used?
+// -   index++ increments by 1 each time the lope find a match. Without index would stay at 0 and the loop would never stop.
 // d) What is the condition index < str.length used for?
+// -   To check the number of characters in str. Once index equals str.length and every characters is checked the loop stops
diff --git a/sprint-3-stretch-exercises/password-validator.js b/sprint-3-stretch-exercises/password-validator.js
index ac70324a5..e0e048381 100644
--- a/sprint-3-stretch-exercises/password-validator.js
+++ b/sprint-3-stretch-exercises/password-validator.js
@@ -1,3 +1,16 @@
-export function isValidPassword(password) {
-  return password.length >= 5;
+export function isValidPassword(password, previousPasswords = []) {
+  if (previousPasswords.includes(password)) {
+    return false;
+  }
+
+  if (password.length < 5) {
+    return false;
+  }
+
+  if (!/[A-Z]/.test(password)) return false;
+  if (!/[a-z]/.test(password)) return false;
+  if (!/[0-9]/.test(password)) return false;
+  if (!/[!#$%.*&]/.test(password)) return false;
+
+  return true;
 }
diff --git a/sprint-3-stretch-exercises/password-validator.test.js b/sprint-3-stretch-exercises/password-validator.test.js
index 2a58a0fb6..9b799f51c 100644
--- a/sprint-3-stretch-exercises/password-validator.test.js
+++ b/sprint-3-stretch-exercises/password-validator.test.js
@@ -16,11 +16,62 @@ You must breakdown this problem in order to solve it. Find one test case first a
 */
 import { isValidPassword } from "./password-validator.js";
 test("password has at least 5 characters", () => {
-    // Arrange
-    const password = "12345";
-    // Act
-    const result = isValidPassword(password);
-    // Assert
-    expect(result).toEqual(true);
-}
-);
\ No newline at end of file
+  // Arrange
+  const password = "Az9!";
+  // Act
+  const result = isValidPassword(password);
+  // Assert
+  expect(result).toEqual(false);
+});
+
+// Have at least one English uppercase letter (A-Z)
+test("password has at least uppercase letter", () => {
+  const password = "1az9!";
+  const result = isValidPassword(password);
+  expect(result).toEqual(false);
+});
+
+// Have at least one English lowercase letter (a-z)
+test("password has at least lowercase letter", () => {
+  const password = "1AZ9!";
+  const result = isValidPassword(password);
+  expect(result).toEqual(false);
+});
+
+// Have at least one number (0-9)
+test("password has at least one number (0-9)", () => {
+  const password = "Aazc!";
+  const result = isValidPassword(password);
+  expect(result).toEqual(false);
+});
+
+// Have at least one of the following non-alphanumeric symbols: ("!", "#", "$", "%", ".", "*", "&")
+test("password has at least non-alphanumeric symbols", () => {
+  const password = "1Az99";
+  const result = isValidPassword(password);
+  expect(result).toEqual(false);
+});
+
+//  Must not be any previous password in the passwords array.
+test("password must not be any previous password in the passwords array", () => {
+  const password = "1Az9!";
+
+  const previousPassword1 = ["1Az9!", "1HBz2!"];
+  const result1 = isValidPassword(password, previousPassword1);
+  expect(result1).toEqual(false);
+
+  const previousPassword2 = ["1HBz2!", "1Az9!"];
+  const result2 = isValidPassword(password, previousPassword2);
+  expect(result2).toEqual(false);
+
+  const previousPassword3 = ["1Az8!", "1HBz2!"];
+  const result3 = isValidPassword(password, previousPassword3);
+  expect(result3).toEqual(true);
+});
+
+// Valid password returns true.
+test("valid password returns true", () => {
+  const password = "1Az9!";
+  const result = isValidPassword(password);
+  expect(result).toEqual(true);
+});