Can community or junior athletes be drug tested?

Yes. Sport Integrity Australia (SIA) says that under clause 1.06 of the National Anti-Doping scheme, any athlete who competes in a sport with an anti-doping policy can be tested, so if you play in a code-compliant sport you can be tested at any level. SIA also says anyone signed up to a sports organisation that abides by the National Anti-Doping Rules can be sanctioned for doping, and an athlete can be selected for testing anywhere, any time.

Sports that have adopted the Australian National Anti-Doping Policy include Australian Athletics, Swimming Australia, Hockey Australia, Basketball Australia, Netball Australia, Rugby Australia, Cricket Australia, Tennis Australia, Touch Football Australia, Gymnastics Australia, Golf Australia and Surf Life Saving Australia (Cricket, Tennis and Surf Life Saving have approved variations). Football Australia and the NRL have SIA-approved anti-doping policies, and the AFL is a signatory to the World Anti-Doping Code. SIA keeps the full list at https://www.sportintegrity.gov.au/what-we-do/anti-doping/world-anti-doping-code/sports-anti-doping-policy-or-similar

If you are under 18 and selected for testing, you are encouraged to have a representative present while you provide a sample.

Sources: https://www.sportintegrity.gov.au/what-we-do/anti-doping/athlete-testing/testing-pools and https://www.sportintegrity.gov.au/what-we-do/anti-doping