Changed to use the logic already existing in FieldName property for selection of POCO field's name

I will soon add test for my last pull requests, but I'm a little bit confused. I post here some beginner's questions.

Which branch am I supposed to make changes to? is V3 fixes still merged? or should I use v3 or master?

I noticed there are different places where tests are present. I should add some tests for JoinSqlBuilder class, should I create a new test project for that or I can use one already existing.

and, I saw various strategies for testing inside the code. Is there a testing framework in use for test automation?

Thanks for your help. Regards