A cross in which an organism showing a dominant phenotype is...

In Genetics, a test cross first introduced by Mendel is used to determine, if an individual exhibiting a dominant trait is homozygous or heterozygous for that trait. More simply, test cross determines the genotype of an individual with a dominant phenotype. In some sources, the test cross is defined as being a type of back cross between the recessive homozygote and $\mathrm{F}_1$-generation.