What is the test for a police officer to approach a person in the street without probable cause for arrest?

The nature and extent of the governmental interests involved must be considered. (Terry v. Ohio, supra, 392 U.S. at p. 22.) "One general interest is of course that of effective crime prevention and detection; it is this interest which underlies the recognition that a police officer may in appropriate circumstances and in an appropriate manner approach a person for purposes of investigating possibly criminal behavior even though there is no probable cause to make an arrest." (Ibid.)