Comprehensive and Detailed Explanation From Exact Extract JavaScript knowledge:
First, recall the fizzbuzz rules:
If n divisible by 3 and not by 5 → return 'fizz'.
If n divisible by 5 and not by 3 → return 'buzz'.
If n divisible by both 3 and 5 → return 'fizzbuzz'.
Otherwise → return '' (empty string).
Evaluate each test:
Option A:
let res = fizzbuzz(true);
console.assert(res === '');
In JavaScript, when using arithmetic operations with true, it is coerced to the number 1. A typical implementation of fizzbuzz would treat the argument as a number and compute:
true % 3 → 1 % 3 → 1
true % 5 → 1 % 5 → 1
So true is effectively treated as 1, which is divisible by neither 3 nor 5. The function should return ''. The assertion res === '' will pass.
This test covers the scenario "neither divisible by 3 nor 5".
Option B:
let res = fizzbuzz(3);
console.assert(res === '');
3 is divisible by 3 but not by 5.
According to fizzbuzz rules, fizzbuzz(3) should return 'fizz'.
This test expects '', so it is incorrect; the assertion would fail in a correct implementation.
Option C:
let res = fizzbuzz(5);
console.assert(res === 'fizz');
5 is divisible by 5 but not by 3.
According to fizzbuzz rules, fizzbuzz(5) should return 'buzz'.
This test expects 'fizz', so it is incorrect.
Option D:
let res = fizzbuzz(15);
console.assert(res === 'fizzbuzz');
15 is divisible by both 3 and 5.
According to fizzbuzz rules, fizzbuzz(15) should return 'fizzbuzz'.
This assertion correctly matches the expected result, so it is a proper test case.
Thus, the two test cases that correctly test valid fizzbuzz behavior are:
Study Guide / Concept Reference (no links):
Modulo operator (%) for divisibility checks
Truthy/number coercion of boolean true in arithmetic (Number(true) === 1) Designing unit tests with console.assert Typical fizzbuzz logic structure and expected outputs
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