Buying quality electronic devices
If you're thinking about ISO-9000 that's about the quality of your organization and its processes, not your products. You can have ISO-9000 certification and still produce the worst crap.  

There are certification organizations, like Underwriters Laboratories in the US and TüV (Technischer Überwachungsverein) in Germany. Many components won't have certification, though. You'll find it mostly in safety sensitive components, like where isolation from mains is important.
Other organizations, like IEC (International Electrotechnical Committee) write specifications, but don't certify.

A good manufacturer should hand you its own testing procedures for its components upon request, as well as test reports. Those are sometimes included in datasheets.
Some will refer to certification organization standards, like shown in this snapshot of a random Littelfuse datasheet:  

  

Note that the Underwiters Laboratories (the top logo) and PSE (Product Safety Engineering) logos refer to their respective certification, while the CE logo doesn't imply this. (The CE logo means that you claim to comply with CE standards).