Implement `require_migration!` helper method

The `require_migration!` helper method can be used to require migration
files in our specs.

doc/development/testing_guide/testing_migrations_guide.md

@@ -37,15 +37,37 @@ ensures proper isolation.
 
 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:
+will need to load the migration file by using the `require_migration!` helper
+method because it is not autoloaded by Rails.
+
+Example:
 
 ```ruby
-require Rails.root.join('db', 'post_migrate', '20170526185842_migrate_pipeline_stages.rb')
+require 'spec_helper'
+
+require_migration!
+
+RSpec.describe ...
 ```
 
 ### Test helpers
 
+#### `require_migration!`
+
+Since the migration files are not autoloaded by Rails, you will need to manually
+load the migration file. To do so, you can use the `require_migration!` helper method
+which can automatically load the correct migration file based on the spec file name.
+
+For example, if your spec file is named as `populate_foo_column_spec.rb` then the
+helper method will try to load `${schema_version}_populate_foo_column.rb` migration file.
+
+In case there is no pattern between your spec file and the actual migration file,
+you can provide the migration file name without the schema version, like so:
+
+```ruby
+require_migration!('populate_foo_column')
+```
+
 #### `table`
 
 Use the `table` helper to create a temporary `ActiveRecord::Base`-derived model
@@ -110,7 +132,8 @@ migration. You can find the complete spec in
 
 ```ruby
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20170526185842_migrate_pipeline_stages.rb')
+
+require_migration!
 
 RSpec.describe MigratePipelineStages do
   # Create test data - pipeline and CI/CD jobs.

ee/spec/migrations/add_unique_constraint_to_software_licenses_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191108202723_add_unique_constraint_to_software_licenses.rb')
+require_migration!
 
 RSpec.describe AddUniqueConstraintToSoftwareLicenses do
   let(:migration) { described_class.new }

ee/spec/migrations/backfill_operations_feature_flags_iid_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200117194850_backfill_operations_feature_flags_iid.rb')
+require_migration!
 
 RSpec.describe BackfillOperationsFeatureFlagsIid do
   let(:namespaces)     { table(:namespaces) }

ee/spec/migrations/backfill_software_licenses_spdx_identifiers_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20190917173107_backfill_software_licenses_spdx_identifiers.rb')
+require_migration!
 
 RSpec.describe BackfillSoftwareLicensesSpdxIdentifiers do
   let(:software_licenses) { table(:software_licenses) }

ee/spec/migrations/backfill_version_author_and_created_at_spec.rb

 # frozen_string_literal: true
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191030223057_backfill_version_author_and_created_at.rb')
+require_migration!
 
 RSpec.describe BackfillVersionAuthorAndCreatedAt do
   let_it_be(:migration_name) { described_class::MIGRATION.to_s.demodulize }

ee/spec/migrations/cleanup_deploy_access_levels_for_removed_groups_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191125024005_cleanup_deploy_access_levels_for_removed_groups.rb')
+require_migration!
 
 RSpec.describe CleanupDeployAccessLevelsForRemovedGroups do
   let(:namespaces) { table(:namespaces) }

ee/spec/migrations/fix_any_approver_rule_for_projects_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191008143850_fix_any_approver_rule_for_projects.rb')
+require_migration!
 
 RSpec.describe FixAnyApproverRuleForProjects do
   let(:namespaces) { table(:namespaces) }

ee/spec/migrations/geo/migrate_ci_job_artifacts_to_separate_registry_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('ee', 'db', 'geo', 'migrate', '20180322062741_migrate_ci_job_artifacts_to_separate_registry.rb')
+require_migration!
 
 RSpec.describe MigrateCiJobArtifactsToSeparateRegistry, :geo do
   let(:file_registry) { table(:file_registry) }

ee/spec/migrations/migrate_design_notes_mentions_to_db_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200124110831_migrate_design_notes_mentions_to_db')
+require_migration!
 
 RSpec.describe MigrateDesignNotesMentionsToDb, :sidekiq do
   let(:users) { table(:users) }

ee/spec/migrations/migrate_epic_mentions_to_db_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191115115043_migrate_epic_mentions_to_db')
+require_migration!
 
 RSpec.describe MigrateEpicMentionsToDb, :migration do
   let(:users) { table(:users) }

ee/spec/migrations/migrate_epic_notes_mentions_to_db_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191115115522_migrate_epic_notes_mentions_to_db')
+require_migration!
 
 RSpec.describe MigrateEpicNotesMentionsToDb, :migration do
   let(:users) { table(:users) }

ee/spec/migrations/migrate_saml_identities_to_scim_identities_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200310215714_migrate_saml_identities_to_scim_identities.rb')
+require_migration!
 
 RSpec.describe MigrateSamlIdentitiesToScimIdentities, :migration do
   let(:group1) { table(:namespaces).create!(name: 'group1', path: 'group1') }

ee/spec/migrations/migrate_scim_identities_to_saml_for_new_users_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200506154421_migrate_scim_identities_to_saml_for_new_users.rb')
+require_migration!
 
 RSpec.describe MigrateScimIdentitiesToSamlForNewUsers, :migration do
   let(:group1) { table(:namespaces).create!(name: 'group1', path: 'group1') }

ee/spec/migrations/migrate_vulnerability_dismissal_feedback_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200519201128_migrate_vulnerability_dismissal_feedback.rb')
+require_migration!
 
 RSpec.describe MigrateVulnerabilityDismissalFeedback, :migration, :sidekiq do
   let(:users) { table(:users) }

ee/spec/migrations/migrate_vulnerability_dismissals_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200416111111_migrate_vulnerability_dismissals.rb')
+require_migration!
 
 RSpec.describe MigrateVulnerabilityDismissals, :migration, :sidekiq do
   let(:users) { table(:users) }

ee/spec/migrations/nullify_feature_flag_plaintext_tokens_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191022113635_nullify_feature_flag_plaintext_tokens.rb')
+require_migration!
 
 RSpec.describe NullifyFeatureFlagPlaintextTokens do
   let(:namespaces) { table(:namespaces) }

ee/spec/migrations/remove_creations_in_gitlab_subscription_histories_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200113151354_remove_creations_in_gitlab_subscription_histories.rb')
+require_migration!
 
 RSpec.describe RemoveCreationsInGitlabSubscriptionHistories do
   before do

ee/spec/migrations/schedule_fix_orphan_promoted_issues_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200207185149_schedule_fix_orphan_promoted_issues.rb')
+require_migration!
 
 RSpec.describe ScheduleFixOrphanPromotedIssues do
   let(:projects) { table(:projects) }

ee/spec/migrations/schedule_fix_ruby_object_in_audit_events_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200518114540_schedule_fix_ruby_object_in_audit_events.rb')
+require_migration!
 
 RSpec.describe ScheduleFixRubyObjectInAuditEvents do
   let(:audit_events) { table(:audit_events) }

ee/spec/migrations/schedule_merge_request_any_approval_rule_migration_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20190905091831_schedule_merge_request_any_approval_rule_migration.rb')
+require_migration!
 
 RSpec.describe ScheduleMergeRequestAnyApprovalRuleMigration do
   let(:namespaces) { table(:namespaces) }

ee/spec/migrations/schedule_project_any_approval_rule_migration_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20190905091812_schedule_project_any_approval_rule_migration.rb')
+require_migration!
 
 RSpec.describe ScheduleProjectAnyApprovalRuleMigration do
   let(:namespaces) { table(:namespaces) }

ee/spec/migrations/set_report_type_for_vulnerabilities_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191105094625_set_report_type_for_vulnerabilities.rb')
+require_migration!
 
 RSpec.describe SetReportTypeForVulnerabilities do
   let(:confidence_levels) do

ee/spec/migrations/set_resolved_state_on_vulnerabilities_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191114173624_set_resolved_state_on_vulnerabilities.rb')
+require_migration!
 
 RSpec.describe SetResolvedStateOnVulnerabilities do
   let(:confidence_levels) do

ee/spec/migrations/update_cs_vulnerability_confidence_column_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20190909141517_update_cs_vulnerability_confidence_column.rb')
+require_migration!
 
 RSpec.describe UpdateCsVulnerabilityConfidenceColumn do
   let(:vulnerabilities) { table(:vulnerability_occurrences) }

ee/spec/migrations/update_occurrence_severity_column_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-
-require Rails.root.join('db', 'post_migrate', '20200227140242_update_occurrence_severity_column.rb')
+require_migration!
 
 RSpec.describe UpdateOccurrenceSeverityColumn do
   let(:vulnerabilities) { table(:vulnerability_occurrences) }

ee/spec/migrations/update_undefined_confidence_from_occurrences_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-
-require Rails.root.join('db', 'post_migrate', '20200506085748_update_undefined_confidence_from_occurrences.rb')
+require_migration!
 
 RSpec.describe UpdateUndefinedConfidenceFromOccurrences, :migration do
   let(:vulnerabilities) { table(:vulnerability_occurrences) }

ee/spec/migrations/update_undefined_confidence_from_vulnerabilities_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-
-require Rails.root.join('db', 'post_migrate', '20200511092714_update_undefined_confidence_from_vulnerabilities.rb')
+require_migration!
 
 RSpec.describe UpdateUndefinedConfidenceFromVulnerabilities, :migration do
   let(:vulnerabilities) { table(:vulnerabilities) }

ee/spec/migrations/update_vulnerability_severity_column_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-
-require Rails.root.join('db', 'post_migrate', '20200302142052_update_vulnerability_severity_column.rb')
+require_migration!
 
 RSpec.describe UpdateVulnerabilitySeverityColumn, :migration do
   let(:vulnerabilities) { table(:vulnerabilities) }

spec/support/helpers/require_migration.rb

+# frozen_string_literal: true
+
+require 'find'
+
+class RequireMigration
+  MIGRATION_FOLDERS = %w(db/migrate db/post_migrate ee/db/geo/migrate ee/db/geo/post_migrate).freeze
+  SPEC_FILE_PATTERN = /.+\/(?<file_name>.+)_spec\.rb/.freeze
+
+  class << self
+    def require_migration!(file_name)
+      file_paths = search_migration_file(file_name)
+
+      require file_paths.first
+    end
+
+    def search_migration_file(file_name)
+      MIGRATION_FOLDERS.flat_map do |path|
+        migration_path = Rails.root.join(path).to_s
+
+        Find.find(migration_path).grep(/\d+_#{file_name}\.rb/)
+      end
+    end
+  end
+end
+
+def require_migration!(file_name = nil)
+  location_info = caller_locations.first.path.match(RequireMigration::SPEC_FILE_PATTERN)
+  file_name ||= location_info[:file_name]
+
+  RequireMigration.require_migration!(file_name)
+end