Some minor column reordering
all users have a username
account identifiers need not be longer than 31 chars
Add shoulda-matchers dependency
Ensure the account is provided when saving a line
don't waste time validating the account

The database will do that for us
limit the length of transfer code
don't need to test what happens when code is nil
limit scope to 23 characters
ensure balance and amount columns are not null
range_type and function should not be nil
don't need shoulda-matchers after all
don't need to resort to meta programming

for such little numbers of attributes
minor tidy of the account spec
namespace the spec
cannot define an account with long identifier
Don't need writers for these attributes
namespace the transfer spec
No need for metaprogramming

for so few attributes
Test transfer code length upon definition