The old-fashioned way to test for independent assortment by the two-point testcross involves two steps. First, one determines that there are more parental offspring than recombinant offspring. While it's possible to see the opposite (more recombinant than parental), this can not be explained by linkage; the simplest explanation would be selection favoring the recombinants. The second step is to determine if there are significantly more parental than recombinant offspring, since some deviation from expectations is always expected. If the testcross produced N offspring, one would expect 25% x N of each phenotype. The chi-square test would be performed as before.