We report on our implementation of an algorithm due to Neumann and Praeger
for deciding whether or not a matrix group over a finite field contains
the special linear group. This is a Monte Carlo algorithm, and thus
has a small but precise probability of returning the wrong answer;
this probability can be specified in advance by the user. The algorithm
requires the selection of random elements from the group, and the most
important problem that arose in the implementation was to find a
satisfactory procedure for making this selection.