input: Write a function to format a given piece of text with different options for font-style, size, and color. The function should return the formatted text as an HTML span element.
  
  def format_text(text, font="Times New Roman", size='14px', color='#000000'):
    return "<span style='font-family: {}, font-size: {}, color: {}'>{}</span>".format(font, size, color, text)
  
  assert format_text('Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer ut lectus vel nisi consequat bibendum ac a erat. Aliquam non velit sit amet arcu placerat vulputate a ut nibh.')== "<span style='font-family: Times New Roman, font-size: 14px, color: #000000'>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer ut lectus vel nisi consequat bibendum ac a erat. Aliquam non velit sit amet arcu placerat vulputate a ut nibh.</span>"
  
  assert format_text('Hello World', 'Arial', '20px', '#ff0000')== "<span style='font-family: Arial, font-size: 20px, color: #ff0000'>Hello World</span>"
  
  assert format_text('', 'Verdana', '12px', '#0000ff')== "<span style='font-family: Verdana, font-size: 12px, color: #0000ff'></span>"
output: 
  def format_text(text, font="Times New Roman", size='14px', color='#000000'):
    return "<span style='font-family: {}, font-size: {}, color: {}'>{}</span>".format(font, size, color, text)
  