What is the test for conducting a search incident to arrest?

As L’Heureux-Dubé J. stated in Cloutier [Cloutier v. Langlois, 1990 CanLII 122 (SCC), [1990] 1 S.C.R. 158], the three main purposes of search incident to arrest are ensuring the safety of the police and public, the protection of evidence from destruction at the hands of the arrestee or others, and the discovery of evidence which can be used at the arrestee’s trial. The restriction that the search must be “truly incidental” to the arrest means that the police must be attempting to achieve some valid purpose connected to the arrest. Whether such an objective exists will depend on what the police were looking for and why. There are both subjective and objective aspects to this issue. In my view, the police must have one of the purposes for a valid search incident to arrest in mind when the search is conducted. Further, the officer’s belief that this purpose will be served by the search must be a reasonable one. . . .