Whitney,
The ladies are doing a great job of helping you talk through your testing options.

They are right that there are many different routes you can take for standardized testing.
We have always given the Iowa Basics Skills test at our house, which you can get many places but we do through Bob Jones. You do need a college degree to be able to administer the test, and you must be approved as a test administrator by submitting a copy of your college diploma.

I give the Iowa Basics just because I think it is good practice in test-taking for my kiddos in all areas, and I personally like detailed feedback. However, it is a very long test to administer and does require a substancial amount of my time to give to multiple kiddos in multiple grades!
With that being said, I think there are different reasons for giving standardized tests, and that it is good to know your own goals prior to heading into testing (as your goals will make a difference as to what kind of test is best for you and your child at this particular time).

Goals can change from year-to-year in test taking, so don't worry about keeping the same goals all of the time.
For example, if you are mainly concerned about making sure that your child is showing progress in a few key areas and about making sure that your child does not get test anxiety, you may wish to go with a test like Seton's CAT survey that is shorter, tests only the main areas, and does not cause as much anxiety.

Or, if you desire more specific information about your child in many different areas, don't mind taking several days to test, and aren't worried much about test anxiety due to timed tests; then you may wish to consider something like the Iowa Basic Skills or the CAT5 test.
We've found that it does help to give the same test a couple of years in a row, just to compare results from a similar test from year to year. So, this may be something to consider as well.
Blessings,
Carrie