There are number of tests available that help you provide evidence of your English language ability for lodging a visa. These include: IELTS Academic, PTE (Academic), OET, TOEFL, and Cambridge (CAE).
The minimum scores required for each test are:
IELTS - Overall score 6 with at least 5 in each band
PTE - overall score 50 with at least 36 in each band
OET - a score of at least B in each of the four components
TOEFL - Total score 64 with 4 in listening and reading and at least 14 in writing and speaking
Cambridge – 169 overall with at least 154 in each band