Fizz Buzz TDD with Deno

fizzBuzz.test.ts

import fizzBuzz, { FIZZ, BUZZ, FIZZ_BUZZ } from "./fizzBuzz.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

Deno.test(
  "FizzBuzz should return the same number given if is not divisible by 3 or 5",
  () => {
    assertEquals(fizzBuzz(1), 1);
  },
);
Deno.test(
  'FizzBuzz should return "Fizz" if the number given is divisible by 3',
  () => {
    assertEquals(fizzBuzz(6), FIZZ);
  },
);
Deno.test(
  'FizzBuzz should return "Buzz" if the number given is divisible by 5',
  () => {
    assertEquals(fizzBuzz(25), BUZZ);
  },
);
Deno.test(
  'FizzBuzz should return "FizzBuzz" if the number given is divisible by 5 and 3',
  () => {
    assertEquals(fizzBuzz(15), FIZZ_BUZZ);
  },
);

fizzBuzz.ts

import {
  bgWhite,
  magenta,
  cyan,
  bold,
} from "https://deno.land/std/fmt/colors.ts";

const isDivisibleBy = (x: number) => (y: number) => y % x === 0;
const isDivisibleBy3 = isDivisibleBy(3);
const isDivisibleBy5 = isDivisibleBy(5);
const useBold = (color: Function, text: string): string => bold(color(text));

export const FIZZ = useBold(magenta, "Fizz");
export const BUZZ = useBold(cyan, "Buzz");
export const FIZZ_BUZZ = useBold(bgWhite, FIZZ + BUZZ);

export default function fizzBuzz(num: number): string | number {
  if (isDivisibleBy3(num) && isDivisibleBy5(num)) {
    return FIZZ_BUZZ;
  }

  if (isDivisibleBy3(num)) {
    return FIZZ;
  }

  if (isDivisibleBy5(num)) {
    return BUZZ;
  }

  return num;
}

main.ts

import fizzBuzz from "./fizzBuzz.ts";

Array.from({ length: 100 }).forEach((irrelevant, i) => {
  console.log(fizzBuzz(++i));
});