[1936 May 3, 37:3]   TEST IN CALIFORNIA Landon  and  Hoover  Forces  Will Compete  in  Primary.   SAN FRANCISCO, May 3 (AP).— President Roosevelt, Governor Landon of Kansas and Herbert Hoover wil [sic] get the first Far Western test of their strength as Presidential candidates next Tuesday in California's primary.   Confronting the supporters of the Kansan is a coalition of Republican State leaders seeking to send an uninstructed delegation to the national convention. Among these is a former president Hoover.   The Democrats, split three ways on State leadership and economic policy, avowedly are all for President Roosevelt, but there are three slates of convention candidates.   One of these slates was picked personally by the President. Culbert Olson, State Democratic Chairman, and seven others chosen bolted the slate on the ground it was insufficiently liberal, and an "EPIC" slate was made up, nominally for Upton Sinclair. A Townsendite group then entered a third slate, nominally pledged to Representative John S. McGroarty.   Sinclair supporters have charged the McGroarty slate was put into the field by followers of President Roosevelt in an attempt to split the "liberal" Democratic vote.   Anti-Hoover Republicans have hinted that the uninstructed slate was a covert move to work for the nomination of Hoover.