class ParallelTests::Test::Runner

def tests_in_groups(tests, num_groups, options={})

finds all tests and partitions them into groups 
def tests_in_groups(tests, num_groups, options={})
  tests = find_tests(tests, options)
  tests = if options[:group_by] == :found
    tests.map { |t| [t, 1] }
  else
    with_runtime_info(tests)
  end
  Grouper.in_even_groups_by_size(tests, num_groups, options)
end