Automatically maintain test database schema

* Move check from generated helper to test_help.rb, so that all
  applications can benefit
* Rather than just raising when the test schema has pending migrations,
  try to load in the schema and only raise if there are pending
  migrations afterwards
* Opt out of the check by setting
  config.active_record.maintain_test_schema = false
* Deprecate db:test:* tasks. The test helper is now fully responsible
  for maintaining the test schema, so we don't need rake tasks for this.
  This is also a speed improvement since we're no longer reloading the
  test database on every call to "rake test".

5 files changed, 22 insertions, 25 deletions

diff --git a/guides/source/4_1_release_notes.md b/guides/source/4_1_release_notes.md
index 171572c77c..0de7860f7d 100644
--- a/guides/source/4_1_release_notes.md
+++ b/guides/source/4_1_release_notes.md
@@ -281,6 +281,13 @@ for detailed changes.
 * Add `Application#message_verifier` method to return a message
   verifier. ([Pull Request](https://github.com/rails/rails/pull/12995))
 
+* The `test_help.rb` file which is required by the default generated test
+  helper will automatically keep your test database up-to-date with
+  `db/schema.rb` (or `db/structure.sql`). It raises an error if
+  reloading the schema does not resolve all pending migrations. Opt out
+  with `config.active_record.maintain_test_schema = false`. ([Pull
+  Request](https://github.com/rails/rails/pull/13528))
+
 Action Pack
 -----------
 
@@ -421,6 +428,10 @@ for detailed changes.
 * Deprecated `ConnectionAdapters::SchemaStatements#distinct`,
   as it is no longer used by internals. ([Pull Request](https://github.com/rails/rails/pull/10556))
 
+* Deprecated `rake db:test:*` tasks as the test database is now
+  automatically maintained. See railties release notes. ([Pull
+  Request](https://github.com/rails/rails/pull/13528))
+
 ### Notable changes
 
 * Added `ActiveRecord::Base.to_param` for convenient "pretty" URLs derived from
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index c30b806907..272850d4c5 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -290,6 +290,8 @@ All these configuration options are delegated to the `I18n` library.
 
 * `config.active_record.attribute_types_cached_by_default` sets the attribute types that `ActiveRecord::AttributeMethods` will cache by default on reads. The default is `[:datetime, :timestamp, :time, :date]`.
 
+* `config.active_record.maintain_test_schema` is a boolean value which controls whether Active Record should try to keep your test database schema up-to-date with `db/schema.rb` (or `db/structure.sql`) when you run your tests. The default is true.
+
 The MySQL adapter adds one additional configuration option:
 
 * `ActiveRecord::ConnectionAdapters::MysqlAdapter.emulate_booleans` controls whether Active Record will consider all `tinyint(1)` columns in a MySQL database to be booleans and is true by default.
diff --git a/guides/source/plugins.md b/guides/source/plugins.md
index 8587bd48b2..720ca5d117 100644
--- a/guides/source/plugins.md
+++ b/guides/source/plugins.md
@@ -224,7 +224,6 @@ and migrating the database. First, run:
 ```bash
 $ cd test/dummy
 $ rake db:migrate
-$ rake db:test:prepare
 ```
 
 While you are here, change the Hickwall and Wickwall models so that they know that they are supposed to act
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 165eca739a..33cd3e868b 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -211,31 +211,9 @@ This line of code is called an _assertion_. An assertion is a line of code that
 
 Every test contains one or more assertions. Only when all the assertions are successful will the test pass.
 
-### Preparing your Application for Testing
+### Maintaining the test database schema
 
-Before you can run your tests, you need to ensure that the test database structure is current. For this you can use the following rake commands:
-
-```bash
-$ rake db:migrate
-...
-$ rake db:test:load
-```
-
-The `rake db:migrate` above runs any pending migrations on the _development_ environment and updates `db/schema.rb`. The `rake db:test:load` recreates the test database from the current `db/schema.rb`. On subsequent attempts, it is a good idea to first run `db:test:prepare`, as it first checks for pending migrations and warns you appropriately.
-
-NOTE: `db:test:prepare` will fail with an error if `db/schema.rb` doesn't exist.
-
-#### Rake Tasks for Preparing your Application for Testing
-
-| Tasks                          | Description                                                               |
-| ------------------------------ | ------------------------------------------------------------------------- |
-| `rake db:test:clone`           | Recreate the test database from the current environment's database schema |
-| `rake db:test:clone_structure` | Recreate the test database from the development structure                 |
-| `rake db:test:load`            | Recreate the test database from the current `schema.rb`                   |
-| `rake db:test:prepare`         | Check for pending migrations and load the test schema                     |
-| `rake db:test:purge`           | Empty the test database.                                                  |
-
-TIP: You can see all these rake tasks and their descriptions by running `rake --tasks --describe`
+In order to run your tests, your test database will need to have the current structure. The test helper checks whether your test database has any pending migrations. If so, it will try to load your `db/schema.rb` or `db/structure.sql` into the test database. If migrations are still pending, an error will be raised.
 
 ### Running Tests
 
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index 2f0f3573fb..bca1d36ab7 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -91,6 +91,13 @@ secrets, you need to:
 
 5. Restart your server.
 
+### Changes to test helper
+
+If your test helper contains a call to
+`ActiveRecord::Migration.check_pending!` this can be removed. The check
+is now done automatically when you `require 'test_help'`, although
+leaving this line in your helper is not harmful in any way.
+
 ### Changes in JSON handling
 
 There are a few major changes related to JSON handling in Rails 4.1.