Add multidb application test

I realized I wasn't really testing some of the new rake tasks added so I
built out this new test that uses a multi-db database.yml and allows us
to run create/drop/migrate/schema:dump/schema:load and those that are
namespaced like create:animals. This will make our testing more robust
so we can catch problems quicker and set a good place to add future
tests as these features evolve.

railties/test/application/rake/multi_dbs_test.rb

@@ -0,0 +1,164 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+
+module ApplicationTests
+  module RakeTests
+    class RakeMultiDbsTest < ActiveSupport::TestCase
+      include ActiveSupport::Testing::Isolation
+
+      def setup
+        build_app(multi_db: true)
+        FileUtils.rm_rf("#{app_path}/config/environments")
+      end
+
+      def teardown
+        teardown_app
+      end
+
+      def db_create_and_drop(namespace, expected_database, environment_loaded: true)
+        Dir.chdir(app_path) do
+          output = rails("db:create")
+          assert_match(/Created database/, output)
+          assert_match_namespace(namespace, output)
+          assert File.exist?(expected_database)
+
+          output = rails("db:drop")
+          assert_match(/Dropped database/, output)
+          assert_match_namespace(namespace, output)
+          assert !File.exist?(expected_database)
+        end
+      end
+
+      def db_create_and_drop_namespace(namespace, expected_database, environment_loaded: true)
+        Dir.chdir(app_path) do
+          output = rails("db:create:#{namespace}")
+          assert_match(/Created database/, output)
+          assert_match_namespace(namespace, output)
+          assert File.exist?(expected_database)
+
+          output = rails("db:drop:#{namespace}")
+          assert_match(/Dropped database/, output)
+          assert_match_namespace(namespace, output)
+          assert !File.exist?(expected_database)
+        end
+      end
+
+      def assert_match_namespace(namespace, output)
+        if namespace == "primary"
+          assert_match(/#{Rails.env}.sqlite3/, output)
+        else
+          assert_match(/#{Rails.env}_#{namespace}.sqlite3/, output)
+        end
+      end
+
+      def db_migrate_and_schema_dump_and_load(namespace, expected_database, format)
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "generate", "model", "dog", "name:string"
+          write_models_for_animals
+          rails "db:migrate", "db:#{format}:dump"
+
+          if format == "schema"
+            schema_dump = File.read("db/#{format}.rb")
+            schema_dump_animals = File.read("db/animals_#{format}.rb")
+            assert_match(/create_table \"books\"/, schema_dump)
+            assert_match(/create_table \"dogs\"/, schema_dump_animals)
+          else
+            schema_dump = File.read("db/#{format}.sql")
+            schema_dump_animals = File.read("db/animals_#{format}.sql")
+            assert_match(/CREATE TABLE \"books\"/, schema_dump)
+            assert_match(/CREATE TABLE \"dogs\"/, schema_dump_animals)
+          end
+
+          rails "db:#{format}:load"
+
+          ar_tables = lambda { rails("runner", "p ActiveRecord::Base.connection.tables").strip }
+          animals_tables = lambda { rails("runner", "p AnimalsBase.connection.tables").strip }
+
+          assert_equal '["schema_migrations", "ar_internal_metadata", "books"]', ar_tables[]
+          assert_equal '["schema_migrations", "ar_internal_metadata", "dogs"]', animals_tables[]
+        end
+      end
+
+      def db_migrate_namespaced(namespace, expected_database)
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "generate", "model", "dog", "name:string"
+          write_models_for_animals
+          output = rails("db:migrate:#{namespace}")
+          if namespace == "primary"
+            assert_match(/CreateBooks: migrated/, output)
+          else
+            assert_match(/CreateDogs: migrated/, output)
+          end
+        end
+      end
+
+      def write_models_for_animals
+        # make a directory for the animals migration
+        FileUtils.mkdir_p("#{app_path}/db/animals_migrate")
+        # move the dogs migration if it unless it already lives there
+        FileUtils.mv(Dir.glob("#{app_path}/db/migrate/**/*dogs.rb").first, "db/animals_migrate/") unless Dir.glob("#{app_path}/db/animals_migrate/**/*dogs.rb").first
+        # delete the dogs migration if it's still present in the
+        # migrate folder. This is necessary because sometimes
+        # the code isn't fast enough and an extra migration gets made
+        FileUtils.rm(Dir.glob("#{app_path}/db/migrate/**/*dogs.rb").first) if Dir.glob("#{app_path}/db/migrate/**/*dogs.rb").first
+
+        # change the base of the dog model
+        app_path("/app/models/dog.rb") do |file_name|
+          file = File.read("#{app_path}/app/models/dog.rb")
+          file.sub!(/ApplicationRecord/, "AnimalsBase")
+          File.write(file_name, file)
+        end
+
+        # create the base model for dog to inherit from
+        File.open("#{app_path}/app/models/animals_base.rb", "w") do |file|
+          file.write(<<-EOS
+class AnimalsBase < ActiveRecord::Base
+  self.abstract_class = true
+
+  establish_connection :animals
+end
+EOS
+)
+        end
+      end
+
+      test "db:create and db:drop works on all databases for env" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_create_and_drop namespace, config["database"]
+        end
+      end
+
+      test "db:create:namespace and db:drop:namespace works on specified databases" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_create_and_drop_namespace namespace, config["database"]
+        end
+      end
+
+      test "db:migrate and db:schema:dump and db:schema:load works on all databases" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_migrate_and_schema_dump_and_load namespace, config["database"], "schema"
+        end
+      end
+
+      test "db:migrate and db:structure:dump and db:structure:load works on all databases" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_migrate_and_schema_dump_and_load namespace, config["database"], "structure"
+        end
+      end
+
+      test "db:migrate:namespace works" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_migrate_namespaced namespace, config["database"]
+        end
+      end
+    end
+  end
+end

railties/test/isolation/abstract_unit.rb

@@ -112,22 +112,57 @@ module TestHelpers
         end
       end
 
-      File.open("#{app_path}/config/database.yml", "w") do |f|
-        f.puts <<-YAML
-        default: &default
-          adapter: sqlite3
-          pool: 5
-          timeout: 5000
-        development:
-          <<: *default
-          database: db/development.sqlite3
-        test:
-          <<: *default
-          database: db/test.sqlite3
-        production:
-          <<: *default
-          database: db/production.sqlite3
-        YAML
+      if options[:multi_db]
+        File.open("#{app_path}/config/database.yml", "w") do |f|
+          f.puts <<-YAML
+          default: &default
+            adapter: sqlite3
+            pool: 5
+            timeout: 5000
+          development:
+            primary:
+              <<: *default
+              database: db/development.sqlite3
+            animals:
+              <<: *default
+              database: db/development_animals.sqlite3
+              migrations_paths: db/animals_migrate
+          test:
+            primary:
+              <<: *default
+              database: db/test.sqlite3
+            animals:
+              <<: *default
+              database: db/test_animals.sqlite3
+              migrations_paths: db/animals_migrate
+          production:
+            primary:
+              <<: *default
+              database: db/production.sqlite3
+            animals:
+              <<: *default
+              database: db/production_animals.sqlite3
+              migrations_paths: db/animals_migrate
+          YAML
+        end
+      else
+        File.open("#{app_path}/config/database.yml", "w") do |f|
+          f.puts <<-YAML
+          default: &default
+            adapter: sqlite3
+            pool: 5
+            timeout: 5000
+          development:
+            <<: *default
+            database: db/development.sqlite3
+          test:
+            <<: *default
+            database: db/test.sqlite3
+          production:
+            <<: *default
+            database: db/production.sqlite3
+          YAML
+        end
       end
 
       add_to_config <<-RUBY