All students are required to prove knowledge of the English language for admission and visa. One should clear a secure English Language Test (SELT). SELT is Home Office-approved English test provider. IELTS and Trinity College London are the few boards recognized by UKVI as SELT providers.
If you need to apply for a visa for degree level courses (e.g. bachelors, masters and PhD programmes) you do not need to take a Secure English Language Test (SELT) to study at a Tier 4 Sponsor university. These institutions can decide which exams to accept as proof of English language ability and you will therefore just need to meet their requirements.