What is the test for warrantless searches in the context of the Fourth Amendment?

The underlying constitutional requirement for all searches and seizures is that they be reasonable (New Jersey v. T.L.O. (1985) 469 U.S. 325, [220 Cal.App.3d 1650] 344, 105 S.Ct. 733, 744, 83 L.Ed.2d 720) ⁷ and there is a presumption that one conducted without a warrant is unreasonable, unless it falls within one of the "specifically established and well-delineated exceptions." (Katz v. United States, supra, 389 U.S. 347, 357, 88 S.Ct. 507, 514.)

As noted by the parties in their respective appellate briefs, the searches here were justified in the trial court on grounds of the "consent" exception. This exception provides the warrantless search of property without probable cause will be lawful under the Fourth Amendment when conducted with voluntary, proper consent. (Schneckloth v. Bustamonte (1973) 412 U.S. 218, 219, 93 S.Ct. 2041, 2043, 36 L.Ed.2d 854.)