In OpenERP first we create groups in res.partner object. Then the ` parameter effectively restricts access to that field for users who do not belong to one of the explicitly allowed groups. Field decimal_places must be found in view definition before the test and then first verify the test environment.

Use this function given below

 def fieldrestriction(self):
       
        original_fields = self.res_currency.fields_get(self.cr, self.demo_uid, [])
        form_view = self.res_currency.fields_view_get(self.cr, self.demo_uid, False, 'form')
        view_arch = etree.fromstring(form_view.get('arch'))
        has_group_system = self.res_users.has_group(self.cr, self.demo_uid, GROUP_SYSTEM)
        self.assertFalse(has_group_system, "`demo` user should not belong to the restricted group before the test")
        self.assertTrue('decimal_places' in original_fields, "'decimal_places' field must be properly visible before the test")
        self.assertNotEquals(view_arch.xpath("//field[@name='decimal_places']"), [],
                             "Field 'decimal_places' must be found in view definition before the test")

        self._set_field_groups(self.res_currency, 'decimal_places', GROUP_SYSTEM)

        fields = self.res_currency.fields_get(self.cr, self.demo_uid, [])
        form_view = self.res_currency.fields_view_get(self.cr, self.demo_uid, False, 'form')
        view_arch = etree.fromstring(form_view.get('arch'))
        self.assertFalse('decimal_places' in fields, "'decimal_places' field should be gone")
        self.assertEquals(view_arch.xpath("//field[@name='decimal_places']"), [],
                          "Field 'decimal_places' must not be found in view definition")

        self.erp_system_group.write({'users': [(4, self.demo_uid)]})
        has_group_system = self.res_users.has_group(self.cr, self.demo_uid, GROUP_SYSTEM)
        fields = self.res_currency.fields_get(self.cr, self.demo_uid, [])
        form_view = self.res_currency.fields_view_get(self.cr, self.demo_uid, False, 'form')
        view_arch = etree.fromstring(form_view.get('arch'))
        self.assertTrue(has_group_system, "`demo` user should now belong to the restricted group")
        self.assertTrue('decimal_places' in fields, "'decimal_places' field must be properly visible again")
        self.assertNotEquals(view_arch.xpath("//field[@name='decimal_places']"), [],
                             "Field 'decimal_places' must be found in view definition again")

        self.erp_system_group.write({'users': [(3, self.demo_uid)]})