old_contents: import unittest
  import frappe
  
  from frappe.core.utils import find
  from frappe.custom.doctype.property_setter.property_setter import make_property_setter
  
  
  class TestDBUpdate(unittest.TestCase):
  	def test_db_update(self):
  		doctype = 'User'
  		frappe.reload_doctype('User', force=True)
  		frappe.model.meta.trim_tables('User')
  		make_property_setter(doctype, 'bio', 'fieldtype', 'Text', 'Data')
  		make_property_setter(doctype, 'enabled', 'default', '1', 'Int')
  
  		frappe.db.updatedb(doctype)
  
  		field_defs = get_field_defs(doctype)
  		table_columns = frappe.db.get_table_columns_description('tab{}'.format(doctype))
  
  		self.assertEqual(len(field_defs), len(table_columns))
  
  		for field_def in field_defs:
  			fieldname = field_def.get('fieldname')
  			table_column = find(table_columns, lambda d: d.get('name') == fieldname)
  
  			fieldtype = get_fieldtype_from_def(field_def)
  
  			default = field_def.default if field_def.default is not None else 'NULL'
  
  			self.assertEqual(fieldtype, table_column.type)
  			self.assertIn(table_column.default or 'NULL', [default, "'{}'".format(default), '0'])
  
  def get_fieldtype_from_def(field_def):
  	fieldtuple = frappe.db.type_map.get(field_def.fieldtype, ('', 0))
  	fieldtype = fieldtuple[0]
  	if fieldtype in ('varchar', 'datetime', 'int'):
  		fieldtype += '({})'.format(field_def.length or fieldtuple[1])
  	return fieldtype
  
  def get_field_defs(doctype):
  	meta = frappe.get_meta(doctype, cached=False)
  	field_defs = meta.get_fieldnames_with_value(True)
  	field_defs += get_other_fields_meta(meta)
  	return field_defs
  
  def get_other_fields_meta(meta):
  	default_fields_map = {
  		'name': ('Data', 0),
  		'owner': ('Data', 0),
  		'parent': ('Data', 0),
  		'parentfield': ('Data', 0),
  		'modified_by': ('Data', 0),
  		'parenttype': ('Data', 0),
  		'creation': ('Datetime', 0),
  		'modified': ('Datetime', 0),
  		'idx': ('Int', 8),
  		'docstatus': ('Int', 1)
  	}
  
  	optional_fields = frappe.db.OPTIONAL_COLUMNS
  	if meta.track_seen:
  		optional_fields.append('_seen')
  
  	optional_fields_map = {field: ('Text', 0) for field in optional_fields}
  	fields = dict(default_fields_map, **optional_fields_map)
  	field_map =  [frappe._dict({'fieldname': field, 'fieldtype': _type, 'length': _length}) for field, (_type, _length) in fields.items()]
  
  	return field_map
new_contents: import unittest
  import frappe
  
  from frappe.core.utils import find
  from frappe.custom.doctype.property_setter.property_setter import make_property_setter
  
  
  class TestDBUpdate(unittest.TestCase):
  	def test_db_update(self):
  		doctype = 'User'
  		frappe.reload_doctype('User', force=True)
  		frappe.model.meta.trim_tables('User')
  		make_property_setter(doctype, 'bio', 'fieldtype', 'Text', 'Data')
  		make_property_setter(doctype, 'enabled', 'default', '1', 'Int')
  
  		frappe.db.updatedb(doctype)
  
  		field_defs = get_field_defs(doctype)
  		table_columns = frappe.db.get_table_columns_description('tab{}'.format(doctype))
  
  		self.assertEqual(len(field_defs), len(table_columns))
  
  		for field_def in field_defs:
  			fieldname = field_def.get('fieldname')
  			table_column = find(table_columns, lambda d: d.get('name') == fieldname)
  
  			fieldtype = get_fieldtype_from_def(field_def)
  
  			fallback_default = '0' if field_def.get('fieldtype') in frappe.model.numeric_fieldtypes else 'NULL'
  			default = field_def.default if field_def.default is not None else fallback_default
  
  			self.assertEqual(fieldtype, table_column.type)
  			self.assertIn(table_column.default or 'NULL', [default, "'{}'".format(default)])
  
  def get_fieldtype_from_def(field_def):
  	fieldtuple = frappe.db.type_map.get(field_def.fieldtype, ('', 0))
  	fieldtype = fieldtuple[0]
  	if fieldtype in ('varchar', 'datetime', 'int'):
  		fieldtype += '({})'.format(field_def.length or fieldtuple[1])
  	return fieldtype
  
  def get_field_defs(doctype):
  	meta = frappe.get_meta(doctype, cached=False)
  	field_defs = meta.get_fieldnames_with_value(True)
  	field_defs += get_other_fields_meta(meta)
  	return field_defs
  
  def get_other_fields_meta(meta):
  	default_fields_map = {
  		'name': ('Data', 0),
  		'owner': ('Data', 0),
  		'parent': ('Data', 0),
  		'parentfield': ('Data', 0),
  		'modified_by': ('Data', 0),
  		'parenttype': ('Data', 0),
  		'creation': ('Datetime', 0),
  		'modified': ('Datetime', 0),
  		'idx': ('Int', 8),
  		'docstatus': ('Int', 1)
  	}
  
  	optional_fields = frappe.db.OPTIONAL_COLUMNS
  	if meta.track_seen:
  		optional_fields.append('_seen')
  
  	optional_fields_map = {field: ('Text', 0) for field in optional_fields}
  	fields = dict(default_fields_map, **optional_fields_map)
  	field_map =  [frappe._dict({'fieldname': field, 'fieldtype': _type, 'length': _length}) for field, (_type, _length) in fields.items()]
  
  	return field_map
subject: Add a fallback default