Added `gem` statement to ensure the gem is being used and not the standard library MiniTest.
Added `gem` statement to ensure the gem is being used and not the
standard library MiniTest.

daptiv/minitest-handler-cookbook,josegonzalez/minitest-handler-cookbook,btm/minitest-handler-cookbook,btm/minitest-handler-cookbook,daptiv/minitest-handler-cookbook,josegonzalez/minitest-handler-cookbook