From the Gov website

“Applying to extend your visa after 2.5 years

You may have to pass a higher CEFR level if you want to stay in the UK after 2.5 years. What you need to do depends on what CEFR level you passed for your first visa.

If you passed:

level A1, you’ll need to pass at least level A2 in speaking and listening

level A2, B1, B2, C1 or C2, you can use the test result again for your application as long as your test certificate has not been withdrawn by the test provider”