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thoughtbot--factory_bot/spec
Daniel Colson d0208eda9c
Default use_parent_strategy to true
Background
---

In issues #64 and #66 (from 2010) people expressed surprise
that using the `build` strategy would still `create` any associations.
I remember being similarly surprised by that behavior when I first
started using factory_bot.

The main reason for this behavior is to ensure the built instance will
be valid if there were any foreign key validations
(like `validates_presence_of :user_id`). If we don't save the
associations, there won't be any ids present.

PR #191 (from 2011) offers a workaround for people who don't want
records to be saved automatically. Passing `strategy: :build`
(originally `method: :build`, but later renamed) when declaring the
association will prevent it from being saved when using `build`.

But #191 isn't really a complete solution (as discussed on the PR
after it was merged). `strategy: :build` may do
the right thing when building objects with the `build` strategy, but it
can cause new problems when using the `create` strategy.

A better solution would be something like:
`strategy: <whatever strategy I was already using>`.
PRs #749 and #961 (merged in 2016) introduce something like that,
with the `use_parent_strategy` configuration option.
With this turned on `build` end up being generally [a little faster][]
than `build_stubbed`, since it no longer needs to hit the database for
each association.

[a little faster]: https://gist.github.com/composerinteralia/d4796df9140f431e36f88dfb6fe9733a

I have set `use_parent_strategy` on several projects now. I also added
it to suspenders in thoughtbot/suspenders#952.
On newer projects I have not run into any problems. On existing
projects I have seen the occasional test failure, which are easy enough
to fix by changing `build` to `create`.

Unfortunately I don't think `use_parent_strategy` is widely known,
since it wasn't documented until #1234 (about a month ago).
I also learned in #1234 that the `use_parent_strategy` setting gets
wiped out with `FactoryBot.reload`, which can be problematic when using
factory_bot_rails.

To summarize, we have been exploring having a `build` strategy that uses
`build` all the way down since 2010, but there still isn't a totally
reliable way to get that.

This PR
---

* Default to using the parent strategy for factory_bot 5, as suggested
in #749.
* In the original PR for this (#1240) I had removed
`use_parent_strategy`, but to make the transition smoother I ended up
fixing the reload problem in #1244

Once factory\_bot 5 is released and the dust has settled, it may make
sense to deprecate `use_parent_strategy`, and maybe also the strategy
option for associations.
2019-01-04 19:57:22 -05:00
..
acceptance Do not reset use_parent_strategy on reload 2019-01-04 15:47:32 -05:00
factory_bot Remove problematic did_you_mean spec 2018-12-16 22:48:06 -05:00
support Rubocop: Fix Style/StringLiterals Offenses (#1216) 2018-10-07 21:45:51 -04:00
factory_bot_spec.rb Remove unnecessary spec_helper requires 2018-05-21 18:03:28 +01:00
spec_helper.rb Default use_parent_strategy to true 2019-01-04 19:57:22 -05:00