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Commit 61d3a252 authored by Luke Duncalfe's avatar Luke Duncalfe Committed by Marcia Ramos
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Move spec/migrations/README.md to docs 

Moving all of this good information to our official docs.
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doc/development/README.md
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......@@ -94,6 +94,7 @@ description: 'Learn how to contribute to GitLab.'
- [What requires downtime?](what_requires_downtime.md)
- [SQL guidelines](sql.md) for working with SQL queries
- [Migrations style guide](migration_style_guide.md) for creating safe SQL migrations
- [Testing Rails migrations](testing_guide/testing_migrations_guide.md) guide
- [Post deployment migrations](post_deployment_migrations.md)
- [Background migrations](background_migrations.md)
- [Swapping tables](swapping_tables.md)
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doc/development/background_migrations.md
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......@@ -290,7 +290,9 @@ It is required to write tests for:
- A cleanup migration.
You can use the `:migration` RSpec tag when testing the migrations.
See [README][migrations-readme].
See the
[Testing Rails migrations](testing_guide/testing_migrations_guide.md#testing-a-non-activerecordmigration-class)
style guide.
When you do that, keep in mind that `before` and `after` RSpec hooks are going
to migrate you database down and up, which can result in other background
......
doc/development/migration_style_guide.md
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......@@ -407,10 +407,7 @@ end
## Testing
Make sure that your migration works for databases with data. An
empty database does not guarantee that your migration is correct.
Make sure your migration can be reversed.
See the [Testing Rails migrations](testing_guide/testing_migrations_guide.md) style guide.
## Data migration
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doc/development/testing_guide/testing_levels.md
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......@@ -44,7 +44,7 @@ records should use stubs/doubles as much as possible.
| `config/routes.rb`, `config/routes/` | `spec/routing/` | RSpec | |
| `config/puma.example.development.rb`, `config/unicorn.rb.example` | `spec/rack_servers/` | RSpec | |
| `db/` | `spec/db/` | RSpec | |
| `db/{post_,}migrate/` | `spec/migrations/` | RSpec | More details at [`spec/migrations/README.md`](https://gitlab.com/gitlab-org/gitlab/blob/master/spec/migrations/README.md). |
| `db/{post_,}migrate/` | `spec/migrations/` | RSpec | More details in the [Testing Rails migrations guide](testing_migrations_guide.md). |
| `Gemfile` | `spec/dependencies/`, `spec/sidekiq/` | RSpec | |
| `lib/` | `spec/lib/` | RSpec | |
| `lib/tasks/` | `spec/tasks/` | RSpec | |
......
doc/development/testing_guide/testing_migrations_guide.md 0 → 100644
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---
type: reference
---
# Testing Rails migrations at GitLab
In order to reliably check Rails migrations, we need to test them against
a database schema.
## When to write a migration test
- Post migrations (`/db/post_migrate`) and background migrations
(`lib/gitlab/background_migration`) **must** have migration tests performed.
- If your migration is a data migration then it **must** have a migration test.
- Other migrations may have a migration test if necessary.
## How does it work?
Adding a `:migration` tag to a test signature enables some custom RSpec
`before` and `after` hooks in our
[`spec_helper.rb`](https://gitlab.com/gitlab-org/gitlab/blob/3b29908a64ff729c0cf6d93452fe00ab23079c75/spec%2Fspec_helper.rb#L259)
to run.
A `before` hook will revert all migrations to the point that a migration
under test is not yet migrated.
In other words, our custom RSpec hooks will find a previous migration, and
migrate the database **down** to the previous migration version.
With this approach you can test a migration against a database schema.
An `after` hook will migrate the database **up** and reinstitute the latest
schema version, so that the process does not affect subsequent specs and
ensures proper isolation.
## Testing an `ActiveRecord::Migration` class
To test an `ActiveRecord::Migration` class (i.e., a
regular migration `db/migrate` or a post-migration `db/post_migrate`), you
will need to manually `require` the migration file because it is not
autoloaded with Rails. Example:
```ruby
require Rails.root.join('db', 'post_migrate', '20170526185842_migrate_pipeline_stages.rb')
```
Use the `table` helper to create a temporary `ActiveRecord::Base`-derived model
for a table. [FactoryBot](https://docs.gitlab.com/ee/development/testing_guide/best_practices.html#factories)
**should not** be used to create data for migration specs. For example, to
create a record in the `projects` table:
```ruby
project = table(:projects).create!(id: 1, name: 'gitlab1', path: 'gitlab1')
```
Use the `migrate!` helper to run the migration that is under test. It will not only
run the migration, but will also bump the schema version in the `schema_migrations`
table. It is necessary because in the `after` hook we trigger the rest of
the migrations, and we need to know where to start. Example:
```ruby
it 'migrates successfully' do
# ... pre-migration expectations
migrate!
# ... post-migration expectations
end
```
### Example database migration test
This spec tests the
[`db/post_migrate/20170526185842_migrate_pipeline_stages.rb`](https://gitlab.com/gitlab-org/gitlab/blob/v11.6.5/db/post_migrate/20170526185842_migrate_pipeline_stages.rb)
migration. You can find the complete spec in
[`spec/migrations/migrate_pipeline_stages_spec.rb`](https://gitlab.com/gitlab-org/gitlab/blob/v11.6.5/spec/migrations/migrate_pipeline_stages_spec.rb).
```ruby
require 'spec_helper'
require Rails.root.join('db', 'post_migrate', '20170526185842_migrate_pipeline_stages.rb')
describe MigratePipelineStages, :migration do
# Create test data - pipeline and CI/CD jobs.
let(:jobs) { table(:ci_builds) }
let(:stages) { table(:ci_stages) }
let(:pipelines) { table(:ci_pipelines) }
let(:projects) { table(:projects) }
before do
projects.create!(id: 123, name: 'gitlab1', path: 'gitlab1')
pipelines.create!(id: 1, project_id: 123, ref: 'master', sha: 'adf43c3a')
jobs.create!(id: 1, commit_id: 1, project_id: 123, stage_idx: 2, stage: 'build')
jobs.create!(id: 2, commit_id: 1, project_id: 123, stage_idx: 1, stage: 'test')
end
# Test the up migration.
it 'correctly migrates pipeline stages' do
expect(stages.count).to be_zero
migrate!
expect(stages.count).to eq 2
expect(stages.all.pluck(:name)).to match_array %w[test build]
end
end
```
## Testing a non-`ActiveRecord::Migration` class
To test a non-`ActiveRecord::Migration` test (a background migration),
you will need to manually provide a required schema version. Please add a
schema tag to a context that you want to switch the database schema within.
Example:
```ruby
describe SomeClass, :migration, schema: 20170608152748 do
# ...
end
```
### Example background migration test
This spec tests the
[`lib/gitlab/background_migration/archive_legacy_traces.rb`](https://gitlab.com/gitlab-org/gitlab/blob/v11.6.5/lib/gitlab/background_migration/archive_legacy_traces.rb)
background migration. You can find the complete spec on
[`spec/lib/gitlab/background_migration/archive_legacy_traces_spec.rb`](https://gitlab.com/gitlab-org/gitlab/blob/v11.6.5/spec/lib/gitlab/background_migration/archive_legacy_traces_spec.rb)
```ruby
require 'spec_helper'
describe Gitlab::BackgroundMigration::ArchiveLegacyTraces, :migration, schema: 20180529152628 do
include TraceHelpers
let(:namespaces) { table(:namespaces) }
let(:projects) { table(:projects) }
let(:builds) { table(:ci_builds) }
let(:job_artifacts) { table(:ci_job_artifacts) }
before do
namespaces.create!(id: 123, name: 'gitlab1', path: 'gitlab1')
projects.create!(id: 123, name: 'gitlab1', path: 'gitlab1', namespace_id: 123)
@build = builds.create!(id: 1, project_id: 123, status: 'success', type: 'Ci::Build')
end
context 'when trace file exists at the right place' do
before do
create_legacy_trace(@build, 'trace in file')
end
it 'correctly archive legacy traces' do
expect(job_artifacts.count).to eq(0)
expect(File.exist?(legacy_trace_path(@build))).to be_truthy
described_class.new.perform(1, 1)
expect(job_artifacts.count).to eq(1)
expect(File.exist?(legacy_trace_path(@build))).to be_falsy
expect(File.read(archived_trace_path(job_artifacts.first))).to eq('trace in file')
end
end
end
```
NOTE: **Note:**
These tests do not run within a database transaction, as we use a deletion database
cleanup strategy. Do not depend on a transaction being present.
spec/migrations/README.md
View file @ 61d3a252
# Testing migrations
In order to reliably test a migration, we need to test it against a database
schema that this migration has been written for. In order to achieve that we
have some _migration helpers_ and RSpec test tag, called `:migration`.
If you want to write a test for a migration consider adding `:migration` tag to
the test signature, like `describe SomeMigrationClass, :migration`.
## How does it work?
Adding a `:migration` tag to a test signature injects a few before / after
hooks to the test.
The most important change is that adding a `:migration` tag adds a `before`
hook that will revert all migrations to the point that a migration under test
is not yet migrated.
In other words, our custom RSpec hooks will find a previous migration, and
migrate the database **down** to the previous migration version.
With this approach you can test a migration against a database schema that this
migration has been written for.
The `after` hook will migrate the database **up** and reinstitutes the latest
schema version, so that the process does not affect subsequent specs and
ensures proper isolation.
## Available helpers
Use `table` helper to create a temporary `ActiveRecord::Base` derived model
for a table.
See `spec/support/helpers/migrations_helpers.rb` for all the available helpers.
## Testing a class that is an ActiveRecord::Migration
In order to test a class that is an `ActiveRecord::Migration`, you will need to
manually `require` the migration file because it is not autoloaded with Rails.
Use `migrate!` helper to run the migration that is under test. It will not only
run migration, but will also bump the schema version in the `schema_migrations`
table. It is necessary because in the `after` hook we trigger the rest of
the migrations, and we need to know where to start.
### Example
This spec tests the [`db/post_migrate/20170526185842_migrate_pipeline_stages.rb`](https://gitlab.com/gitlab-org/gitlab-foss/blob/v11.6.5/db/post_migrate/20170526185842_migrate_pipeline_stages.rb) migration. You can find the complete spec on [`spec/migrations/migrate_pipeline_stages_spec.rb`](https://gitlab.com/gitlab-org/gitlab-foss/blob/v11.6.5/spec/migrations/migrate_pipeline_stages_spec.rb).
```ruby
require 'spec_helper'
require Rails.root.join('db', 'post_migrate', '20170526185842_migrate_pipeline_stages.rb')
describe MigratePipelineStages, :migration do
# Create test data - pipeline and CI/CD jobs.
let(:jobs) { table(:ci_builds) }
let(:stages) { table(:ci_stages) }
let(:pipelines) { table(:ci_pipelines) }
let(:projects) { table(:projects) }
before do
projects.create!(id: 123, name: 'gitlab1', path: 'gitlab1')
pipelines.create!(id: 1, project_id: 123, ref: 'master', sha: 'adf43c3a')
jobs.create!(id: 1, commit_id: 1, project_id: 123, stage_idx: 2, stage: 'build')
jobs.create!(id: 2, commit_id: 1, project_id: 123, stage_idx: 1, stage: 'test')
end
# Test the migration.
it 'correctly migrates pipeline stages' do
expect(stages.count).to be_zero
migrate!
expect(stages.count).to eq 2
expect(stages.all.pluck(:name)).to match_array %w[test build]
end
end
```
## Testing a class that is not an ActiveRecord::Migration
To test a class that is not an `ActiveRecord::Migration` (a background migration),
you will need to manually provide a required schema version. Please add a
schema tag to a context that you want to switch the database schema within.
Example: `describe SomeClass, :migration, schema: 20170608152748`.
### Example
This spec tests the [`lib/gitlab/background_migration/archive_legacy_traces.rb`](https://gitlab.com/gitlab-org/gitlab-foss/blob/v11.6.5/lib/gitlab/background_migration/archive_legacy_traces.rb)
background migration. You can find the complete spec on
[`spec/lib/gitlab/background_migration/archive_legacy_traces_spec.rb`](https://gitlab.com/gitlab-org/gitlab-foss/blob/v11.6.5/spec/lib/gitlab/background_migration/archive_legacy_traces_spec.rb)
```ruby
require 'spec_helper'
describe Gitlab::BackgroundMigration::ArchiveLegacyTraces, :migration, schema: 20180529152628 do
include TraceHelpers
let(:namespaces) { table(:namespaces) }
let(:projects) { table(:projects) }
let(:builds) { table(:ci_builds) }
let(:job_artifacts) { table(:ci_job_artifacts) }
before do
namespaces.create!(id: 123, name: 'gitlab1', path: 'gitlab1')
projects.create!(id: 123, name: 'gitlab1', path: 'gitlab1', namespace_id: 123)
@build = builds.create!(id: 1, project_id: 123, status: 'success', type: 'Ci::Build')
end
context 'when trace file exsits at the right place' do
before do
create_legacy_trace(@build, 'trace in file')
end
it 'correctly archive legacy traces' do
expect(job_artifacts.count).to eq(0)
expect(File.exist?(legacy_trace_path(@build))).to be_truthy
described_class.new.perform(1, 1)
expect(job_artifacts.count).to eq(1)
expect(File.exist?(legacy_trace_path(@build))).to be_falsy
expect(File.read(archived_trace_path(job_artifacts.first))).to eq('trace in file')
end
end
end
```
## Best practices
1. Note that this type of tests do not run within the transaction, we use
a deletion database cleanup strategy. Do not depend on transaction being
present.
This document was moved to [another location](https://docs.gitlab.com/ee/development/testing_guide/testing_migrations_guide.html).
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