Add repeatStr tests and implementation using tdd

Author: remimarcelle

Sprint-3/2-practice-tdd/repeat-str.js

@@ -1,7 +1,26 @@
-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";
+/**
+ * Repeats a string a given number of times.
+ * This re-implements String.prototype.repeat without using it.
+ *
+ * @param {string} str - The string to repeat.
+ * @param {number} count - How many times to repeat it. Must be 0 or greater.
+ * @returns {string} The string repeated count times, or "" if count is 0.
+ * @throws {Error} If count is negative.
+ *
+ * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for
+ */
+function repeatStr(str, count) {
+  if (count < 0) {
+    throw new Error("count must be 0 or greater");
+  }
+
+  let result = "";
+
+  for (let i = 1; i < count; i++) {
+    result = result + str;
+  }
+
+  return result;
 }
 
 module.exports = repeatStr;

Sprint-3/2-practice-tdd/repeat-str.test.js

@@ -20,13 +20,28 @@ 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 = "hello";
+  const count = 1;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("hello");
+});
 
 // 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 = "hello";
+  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 when count is negative", () => {
+  expect(() => repeatStr("hello", -1)).toThrow();
+});