An aqueous solution of copper sulphate, sodium hydroxide, potassium sodium tartarate is called the Fehling’s reagent.
Fehling’s reagent is used for reducing sugars and not specific for aldehydes.
Fructose is a reducing sugar with one free ketone group. It reduces Fehling’s solution giving brick red precipitate.
Fructose under alkaline condition converted to glucose and mannose by keto-enol tautomerism giving positive to Fehling’s solution.