get-ordinal-number.test.js

const getOrdinalNumber = require("./get-ordinal-number");
// 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.
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");
});

// Case 2: Numbers ending in 2 → add nd → (2nd, 22nd, 42nd)
test("should append 'nd' for numbers ending with 2", () => {
  expect(getOrdinalNumber(2)).toEqual("2nd");
  expect(getOrdinalNumber(22)).toEqual("22nd");
  expect(getOrdinalNumber(142)).toEqual("142nd");
});
// Case 3: Numbers ending in 3 → add rd → (3rd, 23rd, 53rd)
test("should append '3rd' for numbers ending with 3", () => {
  expect(getOrdinalNumber(3)).toEqual("3rd");
  expect(getOrdinalNumber(33)).toEqual("33rd");
  expect(getOrdinalNumber(153)).toEqual("153rd");
});
// Case 4: All other numbers → add th → (4th, 6th, 20th, 100th)
test("should append 'th' for numbers ending with 4,5,6,7,8,9 and 0", () => {
  expect(getOrdinalNumber(4)).toEqual("4th");
  expect(getOrdinalNumber(20)).toEqual("20th");
  expect(getOrdinalNumber(100)).toEqual("100th");
});
// Exceptions: Numbers ending in 11, 12, and 13 use -th (e.g., 11th, 12th, 13th). 
test("should append 'th' for numbers ending with 11, 12 and 13", () => {
  expect(getOrdinalNumber(11)).toEqual("11th");
  expect(getOrdinalNumber(12)).toEqual("12th");
  expect(getOrdinalNumber(113)).toEqual("113th");
});