Do employers make you take a drug test before they run your background tests?

I am wondering if a company would bother sending you out for a drug test before you background tests were complete. I had two interviews and then signed a paper saying they could do a background test. About 5 days later they contacted me via email asking me to take a drug test, does this mean I passed the background test? My driving record and criminal record are good, credit no so much, but think they wouldn't waste their time sending me for a drug test if something in there was not good? Does this mean I have passed all of those checks?