Exercise 3: Testing computeFullPath() — Possible Solution
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THE FUNCTION UNDER TEST
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async function computeFullPath(pool, slug, parentId) {
  if (!parentId) return slug;
  const [rows] = await pool.query('SELECT full_path FROM pages WHERE id = ?', [parentId]);
  return `${rows[0].full_path}/${slug}`;
}

TEST 1 — A ROOT PAGE
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await computeFullPath(pool, 'programming', null);
// resolves to 'programming'

The early return fires immediately since parentId is null - no query
is issued to the database at all.

TEST 2 — A NESTED PAGE
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Given a page already stored with id: 1 and full_path: 'programming':

await computeFullPath(pool, 'java', 1);
// resolves to 'programming/java'

The parameterized query fetches that row's own full_path, and the
new page's slug is appended to it with a single slash.

WHY THIS WORKS AS AN ANSWER
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It correctly traces both branches of computeFullPath() - the
no-parent early return and the real-parent parameterized query - and
correctly shows the resulting full_path value each one produces.