There is a test called the Test of English as a Foreign Language (TOEFL) which is widely taken by people who wish to study in the US.

A free TOEFL course starts today.

As you also can read on the above linked page, EdX (Education X) and ETSX (Educational Testing Service X) seem also to be offering the TOEFL iBT (Internet Based Test) take it at home test for free due to the pandemic.

In addition to the EdX test prep course and the TOEFL iBT, I suggest reading stuff that's both (1) short and (2) very famous. For example, in politics, Lincoln's Gettysburg Address and the Declaration of Independence. For short stories, maybe "A Dissertation on Roast Pig," by Charles Lamb and "The Lady, or the Tiger?" by Frank Stockton. For poems, maybe "The Road Not Taken," by Robert Frost, and "Invictus," by William Earnest Henley. For computer folks, "Reflections on Trusting Trust," by Ken Thompson.