Formats and concentration
What is a perfume tester bottle
A perfume tester bottle usually refers to a bottle intended for product demonstration, while some sellers also use tester for small sample formats. Read the exact listing: the word alone does not establish size, packaging, provenance or value.
A HUME Fragrance buying guide

Check what tester means there
A full demonstration bottle and a small spray sample are different offers. Look at the stated millilitres and contents rather than inferring the format from one word.
Verify identity and seller claims
A tester label does not prove authenticity or guarantee identical packaging to a retail bottle. Review the maker, version and seller information.
Compare the complete offer
Check closures, included packaging and order terms if those matter to you. A lower price is only useful when you understand exactly what is supplied.
Try this before you buy
Record the listed size, maker and supplied contents before deciding whether a tester listing matches your need.