Intact peptide bond is necessary for which test

Ninhydrin test and diazo reactions can identify individual amino acid, e.g. diazo reaction is given by histidine or tyrosine. So, an intact peptide bond is not necessary for this reaction, as they can be positive with an individual amino acid. UV diffraction is used to identify higher order structure (secondary, tertiary, quaternary). Thus, non-covalent, as well as covalent (peptide) bonds should be intact.