Individual of unknown genotype crossed with recessive parent.
AII dominant in progeny-Homozygosity, dominant to recessive ratio 1 : 1 in progeny heterozygous.
Detailed Answer :
Test-cross helps to determine the unknown genotype by crossing it with the recessive parent. If in the progeny all are dominant type then the individual is homozygous and if in the Progeny dominant to recessive ratio is 1 : 1, the individual is heterozygous.