To build on
CR001's clear answer above, keep in mind that naturalisation is not a part of the immigration pathway, which ends at ILR, but has it's own separate laws, rules and requirements.
So, even if the English language test or the LITUK test was not required at ILR (such as for refugees and their families or people under the EU Settled Status scheme), those two tests are still required, even for those exempt from the tests at ILR.
The requirements for the English language test are very specific. Either a degree taught in the UK or a degree taught abroad which has been assessed by ECCTIS or a score of at least B1 at an
approved SELT centre.
Both the last two options cost the same (~£150). The latter (SELT centre tests) tend to give a result faster than the former (ECCTIS evaluation).
Keep in mind that these requirements apply even to people who have worked for years in the UK, and even to those who have done their schooling in the UK at GCSE and A levels, but have not yet got a degree.
I am not a lawyer or immigration advisor. My statements/comments do not constitute legal advice. E&OE. Please do not PM me for advice.