In the offspring resulting from an f1 testcross, what percentage of recombinant phenotypes is expected if the genes under study are independently assorting?

A testcross is used to predict the genotype of an organism. It determines whether the genotype of an organism is homozygous or heterozygous.
If the genes under the study are independently assorted then genotype of the F1 generation will  be:

AA for dominant homozygous parent  X  aa for recessive homozygous parent
F1 = All four progeny with Aa genotype

Cross between offspring resulting from F1 testcross will produce:

Aa  X Aa
F2 = One progeny with AA, one progeny with aa, two progeny with Aa (recombinant)
In the offspring resulting from an F1 testcross,  "50%" of recombinant phenotypes is expected if the genes under study are independently assorting.