The mailers expect serializable arguments, but were given
ActiveRecord::Relation objects instead. This made the mailers throw an
exception.
But how was that possible ? This code is tested, and the tests were
green.
Well, the specs spy on the mailer implementation, in order to check that
the mailers methods were properly called. Fair enough.
But if the specs mock the mailer code (instead of calling the original
implementation), we may not notice that the original implementation
rejects our method parameters.
Here this is the case: once we actually call the original implementation
the tests start to fail, because some arguments are not converted from
an ActiveRecord::Relation to a serializable array.
This is fixed by ensuring that the mailer code is executed (and doesn't
throw an exception).
Test helpers are separated between two files: spec_helper and
rails_helper. This separation is meant to allow tests that do not
require Rails (like testing standalone libs) to boot faster.
The spec_helper file is always loaded, through `--require spec_helper`
in the `.rspec` config file. When needed, the rails_helper file is
expected to be required manually.
This is fine, but:
- Many test files have a redundant `require 'spec_helper'` line;
- Many test files should require `rails_helper`, but don't.
Not requiring `rails_helper` will cause the Rails-concerned section of
the test environment not to be configured–which may cause subtle bugs
(like the test database not being properly initialized).
Moreover, Spring loads all the Rails files on preloading anyway. So the
gains from using only `spec_helper` are thin.
To streamline this process, this commit:
- Configures `.rspec` to require `rails_helper` by default;
- Remove all manual requires to spec_helper or rails_helper.
Reference: https://stackoverflow.com/questions/24145329/how-is-spec-rails-helper-rb-different-from-spec-spec-helper-rb-do-i-need-it
