Q. Is every one supposed to taste on Erev Shabbos the foods prepared for Shabbos, or is it enough if one person tastes them? Do all foods have to be tested?

A. It would seem that it depends on the reason why the tasting is done (see prior question – Nishmas Shabbos135). Mishna Berura (250: 2) quoting Magen Avrohom, Shulchan Aruch Horav (250: 8), Mishnas Chasidim (day six), Shulchan Shlomo and others, maintain that all foods should be tasted. Likutey Mahariach and Nimukei Horach Chaim (quoted in Nishmas Shabbos ibid.) explain why even the greater tzadikim would not themselves sample each food, since they relayed on the checking done by the ones that cooked or were in charge of the kitchen. They would usually only taste one particular food to comply with the other aspects involved in this mitzva. Tikunei Shabbos, Reishis Chochmo, Sidur Hashlo (7) quoting the Zohar (Bereishis p. 48) and others opine that the mitzva is on Shabbos itself (Friday night).
Horav Shlomo Miller’s Shlit’a opinion is that there are different minhogim, but in principle it is enough if one person checks the food.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a