Take a look at the UKBA webpage here called - English language requirement

Also, please do review the UKBA list of approved English Language Tests UKBA list of approved English Language Tests

You'll see there's quite a selection of different tests available.

The UKBA site states that:-
"In the test, you will need to demonstrate a basic command of English (speaking and listening) at level A1 of the Common European Framework of Reference.
Someone assessed at level A1 can understand and use simple, everyday expressions and very basic phrases.
You will not need to demonstrate reading, writing or grammar skills.

Plenty of forum members have taken a TOEIC test which is done by Hopkins.
Many members have also taken IELTS
Do be aware that IELTS is a slightly higher level (B1) so if you're not confident with your English that might be quite a stretch.

Many of the test centres can accommodate review classes for those whose self-confidence needs a boost.

Please do take some time to read the forum thread here called - All New Guide - How to apply for a Spouse/Partner Visa

If you follow all the links included you find the answers to many of your general questions