FAR 23.207 provides some useful background.
As always, one needs to read the relevant AC to find out what the rule might actually mean in practical FAA-speak. AC 23-8C indicates -
4. § 23.207 Stall Warning.
a. Explanation.
(1) Purpose. The purpose of this requirement is to ensure an effective warning in sufficient time to allow a pilot to recover from an approach to a stall without reaching the stall.
(2) Types of Warning. The effective warning may be from either aerodynamic disturbances or from a reliable artificial stall-warning device such as a horn or a stick shaker. The aerodynamic warning is usually manifested by a buffet, which vibrates or shakes the airplane. The type of warning should be the same for all configurations.
(3) Artificial Stall Warning. Stall warning devices may be used in cases where there is inadequate aerodynamic warning. The warning signal from the devices should be clear and distinctive and not require the pilot's attention to be directed inside the airplane. A stall warning light by itself is not acceptable. If a stick shaker is installed, the warning should be unmistakable even if flying hands off.
(4) Margin. The stall warning margin, as defined in the rule, is applicable with speed reduced at a rate of one knot per second for §§ 23.201 and 23.203(a)(1).
b. Procedures.
The stall warning tests should be conducted in conjunction with the stall tests required by §§ 23.201 and 23.203.
I'll leave it to those interested to research older versions for any differences applicable to a specific Type/Model Certification.