test vs tester

test and tester both are nouns.

Word	Noun	Adjective	Verb	Adverb
test	Yes	No	Yes	No
tester	Yes	No	No	No

test (noun)	tester (noun)
the act of testing something	a flat canopy (especially one over a four-poster bed)
any standardized procedure for measuring sensitivity or memory or intelligence or aptitude or personality etc	someone who administers a test to determine your qualifications
the act of undergoing testing
a hard outer covering as of some amoebas and sea urchins
trying something to find out about it
a set of questions or exercises evaluating skill or knowledge

test (verb)	tester (verb)
undergo a test
examine someone's knowledge of something
determine the presence or properties of (a substance)
achieve a certain score or rating on a test
put to the test, as for its quality, or give experimental use to
test or examine for the presence of disease or infection
show a certain characteristic when tested