diff --git a/Sprint-3/2-practice-tdd/count.js b/Sprint-3/2-practice-tdd/count.js
index 95b6ebb7d4..888f7bb5d5 100644
--- a/Sprint-3/2-practice-tdd/count.js
+++ b/Sprint-3/2-practice-tdd/count.js
@@ -1,5 +1,50 @@
+/**
+ * countChar(stringOfCharacters, findCharacter)
+ *
+ * Count the number of times a single character appears in a string.
+ *
+ * Behaviour / contract:
+ * - The function is case-sensitive: 'a' ≠ 'A'.
+ * - `stringOfCharacters` may be `null` or `undefined`; in that case the function returns 0.
+ * - `findCharacter` is treated as a single character (a single Unicode code point).
+ *   If you pass a longer string it will never match.
+ *
+ * Parameters:
+ * @param {string|null|undefined} stringOfCharacters - The string to search through.
+ * @param {string} findCharacter - The single character to count (should be length 1).
+ *
+ * Returns:
+ * @returns {number} The number of occurrences of `findCharacter` in `stringOfCharacters`.
+ *
+ * Throws:
+ * - Does not throw for `null`/`undefined` source; returns 0.
+ * - If you want stricter validation for types or for multi-character `findCharacter`,
+ *   validate and throw in the implementation and update tests accordingly.
+ *
+ * Examples:
+ * // basic
+ * countChar('aaaaa', 'a'); // 5
+ * countChar('Hello', 'l'); // 2
+ *
+ * // empty/absent inputs
+ * countChar('', 'a'); // 0
+ * countChar(null, 'a'); // 0
+ *
+ * Notes:
+ * - Uses strict equality (===) so it matches exact code points.
+ * - For emoji or other characters outside the BMP this implementation (for..of)
+ *   iterates code points, which handles many emoji correctly.
+ */
+
 function countChar(stringOfCharacters, findCharacter) {
-  return 5
+  if (stringOfCharacters == null) return 0;
+  let count = 0;
+  for (const char of stringOfCharacters) {
+    if (char === findCharacter) {
+      count++;
+    }
+  }
+  return count;
 }
 
 module.exports = countChar;
diff --git a/Sprint-3/2-practice-tdd/count.test.js b/Sprint-3/2-practice-tdd/count.test.js
index 179ea0ddf7..d5da9a01ce 100644
--- a/Sprint-3/2-practice-tdd/count.test.js
+++ b/Sprint-3/2-practice-tdd/count.test.js
@@ -22,3 +22,22 @@ test("should count multiple occurrences of a character", () => {
 // And a character `char` that does not exist within `str`.
 // When the function is called with these inputs,
 // Then it should return 0, indicating that no occurrences of `char` were found.
+test("return 0 when the character is not found", () => {
+  const str = "hello world";
+  const char = "x";
+  const count = countChar(str, char);
+  expect(count).toEqual(0);
+});
+
+test("handles empty source string", () => {
+  const str = "";
+  const char = "a";
+  const count = countChar(str, char);
+  expect(count).toEqual(0);
+});
+
+test("handles null or undefined source string", () => {
+  const char = "a";
+  expect(countChar(null, char)).toEqual(0);
+  expect(countChar(undefined, char)).toEqual(0);
+});
diff --git a/Sprint-3/2-practice-tdd/get-ordinal-number.js b/Sprint-3/2-practice-tdd/get-ordinal-number.js
index f95d71db13..c470ad54f8 100644
--- a/Sprint-3/2-practice-tdd/get-ordinal-number.js
+++ b/Sprint-3/2-practice-tdd/get-ordinal-number.js
@@ -1,5 +1,25 @@
 function getOrdinalNumber(num) {
-  return "1st";
+  // Validate input: must be a number (not a string, null or undefined) and not NaN
+  if (typeof num !== "number" || Number.isNaN(num)) {
+    throw new TypeError("Input must be a number");
+  }
+
+  const abs = Math.abs(num);
+  const lastTwoDigits = abs % 100;
+  if (lastTwoDigits >= 11 && lastTwoDigits <= 13) {
+    return `${num}th`;
+  }
+  const lastDigit = lastTwoDigits % 10;
+  if (lastDigit === 1) {
+    return `${num}st`;
+  }
+  if (lastDigit === 2) {
+    return `${num}nd`;
+  }
+  if (lastDigit === 3) {
+    return `${num}rd`;
+  }
+  return `${num}th`;
 }
 
 module.exports = getOrdinalNumber;
diff --git a/Sprint-3/2-practice-tdd/get-ordinal-number.test.js b/Sprint-3/2-practice-tdd/get-ordinal-number.test.js
index adfa58560f..4e9284a242 100644
--- a/Sprint-3/2-practice-tdd/get-ordinal-number.test.js
+++ b/Sprint-3/2-practice-tdd/get-ordinal-number.test.js
@@ -13,8 +13,61 @@ const getOrdinalNumber = require("./get-ordinal-number");
 // Case 1: Numbers ending with 1 (but not 11)
 // When the number ends with 1, except those ending with 11,
 // Then the function should return a string by appending "st" to the number.
-test("should append 'st' for numbers ending with 1, except those ending with 11", () => {
-  expect(getOrdinalNumber(1)).toEqual("1st");
-  expect(getOrdinalNumber(21)).toEqual("21st");
-  expect(getOrdinalNumber(131)).toEqual("131st");
+test("should append 'st' for numbers ending with 1, excluding 11", () => {
+  expect(getOrdinalNumber(1)).toBe("1st");
+  expect(getOrdinalNumber(21)).toBe("21st");
+  expect(getOrdinalNumber(101)).toBe("101st");
+  expect(getOrdinalNumber(131)).toBe("131st");
+});
+
+test("should append 'nd' for numbers ending with 2, excluding 12", () => {
+  expect(getOrdinalNumber(2)).toBe("2nd");
+  expect(getOrdinalNumber(22)).toBe("22nd");
+  expect(getOrdinalNumber(132)).toBe("132nd");
+});
+
+test("should append 'rd' for numbers ending with 3, excluding 13", () => {
+  expect(getOrdinalNumber(3)).toBe("3rd");
+  expect(getOrdinalNumber(23)).toBe("23rd");
+  expect(getOrdinalNumber(133)).toBe("133rd");
+});
+
+test("should append 'th' for numbers ending with 11, 12, or 13", () => {
+  expect(getOrdinalNumber(11)).toBe("11th");
+  expect(getOrdinalNumber(12)).toBe("12th");
+  expect(getOrdinalNumber(13)).toBe("13th");
+  expect(getOrdinalNumber(111)).toBe("111th");
+  expect(getOrdinalNumber(112)).toBe("112th");
+  expect(getOrdinalNumber(113)).toBe("113th");
+});
+
+test("should append 'th' for numbers ending with 4-9 or 0", () => {
+  expect(getOrdinalNumber(4)).toBe("4th");
+  expect(getOrdinalNumber(5)).toBe("5th");
+  expect(getOrdinalNumber(6)).toBe("6th");
+  expect(getOrdinalNumber(7)).toBe("7th");
+  expect(getOrdinalNumber(8)).toBe("8th");
+  expect(getOrdinalNumber(9)).toBe("9th");
+  expect(getOrdinalNumber(0)).toBe("0th");
+});
+
+test("non-integer and negative numbers should be handled correctly", () => {
+  expect(getOrdinalNumber(1.5)).toBe("1.5th");
+  expect(getOrdinalNumber(-2.3)).toBe("-2.3th");
+  expect(getOrdinalNumber(-11)).toBe("-11th");
+});
+
+test("invalid input should throw an error", () => {
+  expect(() => getOrdinalNumber("string")).toThrow("Input must be a number");
+  expect(() => getOrdinalNumber(null)).toThrow("Input must be a number");
+  expect(() => getOrdinalNumber(undefined)).toThrow("Input must be a number");
+});
+
+test("NaN input should throw an error", () => {
+  expect(() => getOrdinalNumber(NaN)).toThrow("Input must be a number");
+});
+
+test("Infinity input should be handled correctly", () => {
+  expect(getOrdinalNumber(Infinity)).toBe("Infinityth");
+  expect(getOrdinalNumber(-Infinity)).toBe("-Infinityth");
 });
diff --git a/Sprint-3/2-practice-tdd/repeat-str.js b/Sprint-3/2-practice-tdd/repeat-str.js
index 2af0a2cea7..1564f83d72 100644
--- a/Sprint-3/2-practice-tdd/repeat-str.js
+++ b/Sprint-3/2-practice-tdd/repeat-str.js
@@ -1,7 +1,16 @@
-function repeatStr() {
-  // Your implementation of this function must *not* call String.prototype.repeat (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat).
-  // The goal is to re-implement that function, not to use it.
-  return "hellohellohello";
+function repeatStr(str, count) {
+  if (typeof str !== "string") {
+    throw new TypeError("First argument must be a string");
+  }
+  if (!Number.isInteger(count) || count < 0) {
+    throw new TypeError("Count must be a non-negative integer");
+  }
+
+  let result = "";
+  for (let i = 0; i < count; i++) {
+    result += str;
+  }
+  return result;
 }
 
 module.exports = repeatStr;
diff --git a/Sprint-3/2-practice-tdd/repeat-str.test.js b/Sprint-3/2-practice-tdd/repeat-str.test.js
index a3fc1196c4..12f3cf033e 100644
--- a/Sprint-3/2-practice-tdd/repeat-str.test.js
+++ b/Sprint-3/2-practice-tdd/repeat-str.test.js
@@ -20,13 +20,99 @@ test("should repeat the string count times", () => {
 // Given a target string `str` and a `count` equal to 1,
 // When the repeatStr function is called with these inputs,
 // Then it should return the original `str` without repetition.
-
+test("should return the original string when count is 1", () => {
+  const str = "world";
+  const count = 1;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("world");
+});
 // Case: Handle count of 0:
 // Given a target string `str` and a `count` equal to 0,
 // When the repeatStr function is called with these inputs,
 // Then it should return an empty string.
+test("should return an empty string when count is 0", () => {
+  const str = "test";
+  const count = 0;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("");
+});
 
 // Case: Handle negative count:
 // Given a target string `str` and a negative integer `count`,
 // When the repeatStr function is called with these inputs,
 // Then it should throw an error, as negative counts are not valid.
+test("should throw an error for negative count", () => {
+  const str = "error";
+  const count = -2;
+  expect(() => repeatStr(str, count)).toThrow(
+    "Count must be a non-negative integer"
+  );
+});
+
+test("should throw an error for non-integer count", () => {
+  const str = "error";
+  const count = 2.5;
+  expect(() => repeatStr(str, count)).toThrow(
+    "Count must be a non-negative integer"
+  );
+});
+
+test("should throw an error for non-string input", () => {
+  const str = 123;
+  const count = 3;
+  expect(() => repeatStr(str, count)).toThrow(
+    "First argument must be a string"
+  );
+});
+
+test("should throw an error for null or undefined input", () => {
+  const count = 3;
+  expect(() => repeatStr(null, count)).toThrow(
+    "First argument must be a string"
+  );
+  expect(() => repeatStr(undefined, count)).toThrow(
+    "First argument must be a string"
+  );
+});
+
+test("handle empty string input", () => {
+  const str = "";
+  const count = 5;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("");
+});
+
+test("handle large count input", () => {
+  const str = "a";
+  const count = 1000;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("a".repeat(count));
+});
+
+test("handle special characters in string", () => {
+  const str = "!@#";
+  const count = 4;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("!@#!@#!@#!@#");
+});
+
+test("handle whitespace in string", () => {
+  const str = " ";
+  const count = 3;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("   ");
+});
+
+test("repeats unicode characters correctly", () => {
+  const str = "😊";
+  const count = 5;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("😊😊😊😊😊");
+});
+
+test("handles empty string", () => {
+  const str = "";
+  const count = 5;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("");
+});