pattern.rb

entity = Node.new(id: id)

case
  when not enity.exists? then fail("Entity doesn't exist")
  when not entity.file? then fail("Entity wasn't a file")
  when not entity.writable? then fail("Entity wasn't writable")
  else entity.write(data)
end

pattern2.rb

entity = Node.new(id: id)
 
if enity.exists? && entity.file? && entity.writable?
  entity.write(data)
else
  fail("Entity doesn't exist") unless entity.exists? 
  fail("Entity wasn't a file") unless entity.file?
  fail("Entity wasn't writable") unless entity.writable?
end

pattern3.rb

entity = Node.new(id: id)

class Node
  def write(data)
    fail("Entity doesn't exist") unless exists? 
    fail("Entity wasn't a file") unless file?
    fail("Entity wasn't writable") unless writable?

    # usual write work
  end
end