Being able to communicate in english is a basic requirement for succesaful graduate study in the Australia. If English is not your native language, Australia colleges and universities will ask you to take an English language proficiency test.
The most common tests of English language ability are the Test of English
Test of English as Doreign Language (TOEFL)
International English Language Testing System (IELTS)
ICambridge English Advanced (CAE) test (also known as Certificate in Advanced English), and
Pearson Test of English(PTE)