I don't know about online resources, but I have a test and answer key that I can scan and email to anyone who wants it.
The test comes from my teacher's edition of
Brown's Algebra 2 book. The first 4 chapters of that book review Algebra 1 and the test is provided as a diagnostic aid.
This series of math books is well-respected. I've looked the test over, and it has a solid set of questions. They aren't the toughest problems on the planet, nor are they super-easy unless you really know the subject well. So, overall, a good way to answer the question, "Does the student know this stuff?"
There are 46 questions.
PM me if you want a copy of the test and answer key.
Val