class SimpleCov::SourceFile

def covered_strength
  return 0 if lines.length == 0 or lines.length == never_lines.count
  lines_strength = 0
  lines.each do |c|
    lines_strength += c.coverage if c.coverage
  end
  effective_lines_count = (lines.count - never_lines.count - skipped_lines.count).to_f
  if effective_lines_count == 0
    0
  else
    strength = lines_strength / effective_lines_count
    round_float(strength, 1)
  end
end