Add spec for schema.rb

changelogs/unreleased/spec_for_schema.yml

+---
+title: Add spec for schema.rb
+merge_request: 10580
+author: blackst0ne

spec/migrations/schema_spec.rb

+require 'spec_helper'
+
+# Check consistency of db/schema.rb version, migrations' timestamps, and the latest migration timestamp
+# stored in the database's schema_migrations table.
+
+describe ActiveRecord::Schema do
+  let(:latest_migration_timestamp) do
+    migrations = Dir[Rails.root.join('db', 'migrate', '*'), Rails.root.join('db', 'post_migrate', '*')]
+    migrations.map { |migration| File.basename(migration).split('_').first.to_i }.max
+  end
+
+  it '> schema version equals last migration timestamp' do
+    defined_schema_version = File.open(Rails.root.join('db', 'schema.rb')) do |file|
+      file.find { |line| line =~ /ActiveRecord::Schema.define/ }
+    end.match(/(\d+)/)[0].to_i
+
+    expect(defined_schema_version).to eq(latest_migration_timestamp)
+  end
+
+  it '> schema version should equal the latest migration timestamp stored in schema_migrations table' do
+    expect(latest_migration_timestamp).to eq(ActiveRecord::Migrator.current_version.to_i)
+  end
+end