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8 changes: 7 additions & 1 deletion practice-tdd/count.js
Original file line number Diff line number Diff line change
@@ -1,3 +1,9 @@
export function countChar(stringOfCharacters, findCharacter) {
return 5
let count = 0;
for (const character of stringOfCharacters) {
if (character === findCharacter) {
count++;
}
}
return count;
}
8 changes: 8 additions & 0 deletions practice-tdd/count.test.js

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  • Could consider testing multiple samples in each test category - higher chance to detect bugs in code.

  • Empty string is often a good edge case to test.

  • When a specification is ambiguous, programmers may need to make reasonable assumptions based on their understanding of the requirements. In this case, the original specification did not explicitly state whether character matching should be case-sensitive. Although most people would likely assume that it is, adding test cases can help document this assumption and make our interpretation of the specification explicit.

    Similarly, we should consider adding tests for any other assumptions made during implementation to clarify the intended behavior and ensure these assumptions are consistently understood and validated.

Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
// implement a function countChar that counts the number of times a character occurs in a string
import { countChar } from "./count.js";

// Given a string `str` and a single character `char` to search for,
// When the countChar function is called with these inputs,
// Then it should:
Expand All @@ -22,3 +23,10 @@ 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("should indicate no occurrences of a character", () => {
const str = "abcde";
const char = "f";
const numberOfOccurrence = countChar(str, char);
expect(numberOfOccurrence).toEqual(0);
});
20 changes: 19 additions & 1 deletion practice-tdd/get-ordinal-number.js
Original file line number Diff line number Diff line change
@@ -1,3 +1,21 @@
export function getOrdinalNumber(num) {
return "1st";
//handle a non number inputs
if (!num) {
return "";
}
Comment on lines +2 to +5

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What do you mean by a non-number? !num is not a proper way to check if num is a number or not.

Note: You could assume the parameter is always a number in this exercise.

const lastTwoDigits = num % 100;
// Handle exceptions: 11th, 12th, 13th, 111th, etc.
if (lastTwoDigits >= 11 && lastTwoDigits <= 13) {
return `${num}th`;
}
switch (num % 10) {
case 1:
return `${num}st`;
case 2:
return `${num}nd`;
case 3:
return `${num}rd`;
default:
return `${num}th`;
}
}
56 changes: 51 additions & 5 deletions practice-tdd/get-ordinal-number.test.js

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The tests in this script do not yet covered all valid cases.

Original file line number Diff line number Diff line change
@@ -1,20 +1,66 @@
import { getOrdinalNumber } from "./get-ordinal-number.js";
// In this week's prep, we started implementing getOrdinalNumber.

// In this week's prep, we started implementing getOrdinalNumber.
// Continue testing and implementing getOrdinalNumber for additional cases.
// Write your tests using Jest — remember to run your tests often for continual feedback.

// To ensure thorough testing, we need broad scenarios that cover all possible cases.
// Listing individual values, however, can quickly lead to an unmanageable number of test cases.
// Instead of writing tests for individual numbers, consider grouping all possible input values
// into meaningful categories. Then, select representative samples from each category to test.
// This approach improves coverage and makes our tests easier to maintain.

// 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.
// Case 1:
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");
});

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a test case handling the special cases like 11,12,13,101 & 103 will make this suit more robust.

// Case 2:
test("should append 'nd' for numbers ending with 2, except those ending with 12", () => {
expect(getOrdinalNumber(2)).toEqual("2nd");
expect(getOrdinalNumber(32)).toEqual("32nd");
expect(getOrdinalNumber(72)).toEqual("72nd");
expect(getOrdinalNumber(452)).toEqual("452nd");
expect(getOrdinalNumber(862)).toEqual("862nd");
});

// Case 3: N
test("should append 'rd' for numbers ending with 3, except those ending with 13", () => {
expect(getOrdinalNumber(3)).toEqual("3rd");
expect(getOrdinalNumber(43)).toEqual("43rd");
expect(getOrdinalNumber(93)).toEqual("93rd");
expect(getOrdinalNumber(823)).toEqual("823rd");
expect(getOrdinalNumber(183)).toEqual("183rd");
});

// Case 4:
test("should append 'th' for numbers ending with 4,5,6 ,7 ,8 or 9 ", () => {

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Are all "other digits" covered in this category?

expect(getOrdinalNumber(4)).toEqual("4th");
expect(getOrdinalNumber(25)).toEqual("25th");
expect(getOrdinalNumber(656)).toEqual("656th");
expect(getOrdinalNumber(1007)).toEqual("1007th");
expect(getOrdinalNumber(638398)).toEqual("638398th");
expect(getOrdinalNumber(34454559)).toEqual("34454559th");
});

// Case 5:
test("should append 'th' for numbers in 100's ending with 11, 12 , 13", () => {
expect(getOrdinalNumber(111)).toEqual("111th");
expect(getOrdinalNumber(112)).toEqual("112th");
expect(getOrdinalNumber(113)).toEqual("113th");
});
Comment on lines +48 to +52

@cjyuan cjyuan Oct 28, 2026 •

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Why limit the cases to numbers in the 100's?


// Case 6:A test case handling the special cases like 11,12,13,101 & 103

test("should append 'th' for numbers for 11,12,13 and 'st' for 101 and 'rd' for 103", () => {
expect(getOrdinalNumber(11)).toEqual("11th");
expect(getOrdinalNumber(12)).toEqual("12th");
expect(getOrdinalNumber(13)).toEqual("13th");
expect(getOrdinalNumber(101)).toEqual("101st");
expect(getOrdinalNumber(103)).toEqual("103rd");
});
Comment on lines +54 to +62

@cjyuan cjyuan Oct 28, 2026 •

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Why are these five numbers considered special cases? What do you mean by "special"?


test("should return empty string if empty string is passed", () => {
expect(getOrdinalNumber("")).toEqual("");
});
13 changes: 11 additions & 2 deletions practice-tdd/repeat-str.js
Original file line number Diff line number Diff line change
@@ -1,5 +1,14 @@
export function repeatStr() {
export function repeatStr(str, count) {
// 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";
if (count < 0) {
throw new Error("Error! negative counts are not valid");
}
let result = "";
let counter = count;
while (counter > 0) {
result += str;
counter--;
}
return result;
}
24 changes: 23 additions & 1 deletion practice-tdd/repeat-str.test.js
Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ import { repeatStr } from "./repeat-str.js";
// When the repeatStr function is called with these inputs,
// Then it should return a string that contains the original `str` repeated `count` times.

test("should repeat the string count times", () => {
test("should repeat the string 3 times when the value of count =3", () => {
const str = "hello";
const count = 3;
const repeatedStr = repeatStr(str, count);
Expand All @@ -21,12 +21,34 @@ test("should repeat the string count times", () => {
// 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 the 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 the 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 a negative number.", () => {
const str = "hello";
const count = -3;
expect(() => repeatStr(str, count)).toThrow(
"Error! negative counts are not valid"
);
});
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