Glucose gives silver mirror test with Tollen’s reagent. It shows the presence of

Tollens' test, also known as silver-mirror test, is a test used to distinguish between an aldehyde and a ketone. Formation of silver mirror is the confirmation of the test.

$\mathrm{R}-\mathrm{CHO}+ [\mathrm{Ag}{\left({\mathrm{NH}}_3\right)}_2{]}^{+} \to \mathrm{RCOO}+ \mathrm{Ag}(\mathrm{silver} \mathrm{is} \mathrm{deposited})$