Merge pull request #33637 from eileencodes/ar-connection-management-refactoring

Refactor Active Record configurations

6 files changed, 731 insertions, 74 deletions

diff --git a/activerecord/test/cases/connection_adapters/connection_handler_test.rb b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
index b8e623f17b..8c204a2692 100644
--- a/activerecord/test/cases/connection_adapters/connection_handler_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
@@ -28,13 +28,16 @@ module ActiveRecord
       end
 
       def test_establish_connection_uses_spec_name
+        old_config = ActiveRecord::Base.configurations
         config = { "readonly" => { "adapter" => "sqlite3" } }
-        resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new(config)
+        ActiveRecord::Base.configurations = config
+        resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new(ActiveRecord::Base.configurations)
         spec =   resolver.spec(:readonly)
         @handler.establish_connection(spec.to_hash)
 
         assert_not_nil @handler.retrieve_connection_pool("readonly")
       ensure
+        ActiveRecord::Base.configurations = old_config
         @handler.remove_connection("readonly")
       end
 
diff --git a/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb b/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb
index 1b64324cc4..06c1c51724 100644
--- a/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb
+++ b/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb
@@ -18,11 +18,14 @@ module ActiveRecord
       end
 
       def resolve_config(config)
-        ActiveRecord::ConnectionHandling::MergeAndResolveDefaultUrlConfig.new(config).resolve
+        configs = ActiveRecord::DatabaseConfigurations.new(config)
+        configs.to_h
       end
 
       def resolve_spec(spec, config)
-        ConnectionSpecification::Resolver.new(resolve_config(config)).resolve(spec)
+        configs = ActiveRecord::DatabaseConfigurations.new(config)
+        resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new(configs)
+        resolver.resolve(spec, spec)
       end
 
       def test_resolver_with_database_uri_and_current_env_symbol_key
diff --git a/activerecord/test/cases/connection_specification/resolver_test.rb b/activerecord/test/cases/connection_specification/resolver_test.rb
index 5b80f16a44..72be14f507 100644
--- a/activerecord/test/cases/connection_specification/resolver_test.rb
+++ b/activerecord/test/cases/connection_specification/resolver_test.rb
@@ -7,11 +7,15 @@ module ActiveRecord
     class ConnectionSpecification
       class ResolverTest < ActiveRecord::TestCase
         def resolve(spec, config = {})
-          Resolver.new(config).resolve(spec)
+          configs = ActiveRecord::DatabaseConfigurations.new(config)
+          resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new(configs)
+          resolver.resolve(spec, spec)
         end
 
         def spec(spec, config = {})
-          Resolver.new(config).spec(spec)
+          configs = ActiveRecord::DatabaseConfigurations.new(config)
+          resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new(configs)
+          resolver.spec(spec)
         end
 
         def test_url_invalid_adapter
diff --git a/activerecord/test/cases/legacy_configurations_test.rb b/activerecord/test/cases/legacy_configurations_test.rb
new file mode 100644
index 0000000000..c36feb5116
--- /dev/null
+++ b/activerecord/test/cases/legacy_configurations_test.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+
+module ActiveRecord
+  class LegacyConfigurationsTest < ActiveRecord::TestCase
+    def test_can_turn_configurations_into_a_hash
+      assert ActiveRecord::Base.configurations.to_h.is_a?(Hash), "expected to be a hash but was not."
+      assert_equal ["arunit", "arunit2", "arunit_without_prepared_statements"].sort, ActiveRecord::Base.configurations.to_h.keys.sort
+    end
+
+    def test_each_is_deprecated
+      assert_deprecated do
+        ActiveRecord::Base.configurations.each do |db_config|
+          assert_equal "primary", db_config.spec_name
+        end
+      end
+    end
+
+    def test_first_is_deprecated
+      assert_deprecated do
+        db_config = ActiveRecord::Base.configurations.first
+        assert_equal "arunit", db_config.env_name
+        assert_equal "primary", db_config.spec_name
+      end
+    end
+
+    def test_fetch_is_deprecated
+      assert_deprecated do
+        db_config = ActiveRecord::Base.configurations.fetch("arunit").first
+        assert_equal "arunit", db_config.env_name
+        assert_equal "primary", db_config.spec_name
+      end
+    end
+
+    def test_values_are_deprecated
+      config_hashes = ActiveRecord::Base.configurations.configurations.map(&:config)
+      assert_deprecated do
+        assert_equal config_hashes, ActiveRecord::Base.configurations.values
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/tasks/database_tasks_test.rb b/activerecord/test/cases/tasks/database_tasks_test.rb
index ee53d576a1..a39a7371fe 100644
--- a/activerecord/test/cases/tasks/database_tasks_test.rb
+++ b/activerecord/test/cases/tasks/database_tasks_test.rb
@@ -156,20 +156,24 @@ module ActiveRecord
 
   class DatabaseTasksCreateAllTest < ActiveRecord::TestCase
     def setup
+      @old_configurations = ActiveRecord::Base.configurations
       @configurations = { "development" => { "database" => "my-db" } }
 
       $stdout, @original_stdout = StringIO.new, $stdout
       $stderr, @original_stderr = StringIO.new, $stderr
+
+      ActiveRecord::Base.configurations = @configurations
     end
 
     def teardown
       $stdout, $stderr = @original_stdout, @original_stderr
+      ActiveRecord::Base.configurations = @old_configurations
     end
 
     def test_ignores_configurations_without_databases
       @configurations["development"]["database"] = nil
 
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
           ActiveRecord::Tasks::DatabaseTasks.create_all
         end
@@ -179,7 +183,7 @@ module ActiveRecord
     def test_ignores_remote_databases
       @configurations["development"]["host"] = "my.server.tld"
 
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
           ActiveRecord::Tasks::DatabaseTasks.create_all
         end
@@ -189,7 +193,7 @@ module ActiveRecord
     def test_warning_for_remote_databases
       @configurations["development"]["host"] = "my.server.tld"
 
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         ActiveRecord::Tasks::DatabaseTasks.create_all
 
         assert_match "This task only modifies local databases. my-db is on a remote host.",
@@ -200,7 +204,7 @@ module ActiveRecord
     def test_creates_configurations_with_local_ip
       @configurations["development"]["host"] = "127.0.0.1"
 
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
           ActiveRecord::Tasks::DatabaseTasks.create_all
         end
@@ -210,7 +214,7 @@ module ActiveRecord
     def test_creates_configurations_with_local_host
       @configurations["development"]["host"] = "localhost"
 
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
           ActiveRecord::Tasks::DatabaseTasks.create_all
         end
@@ -220,40 +224,33 @@ module ActiveRecord
     def test_creates_configurations_with_blank_hosts
       @configurations["development"]["host"] = nil
 
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
           ActiveRecord::Tasks::DatabaseTasks.create_all
         end
       end
     end
-
-    private
-
-      def with_stubbed_configurations_establish_connection
-        ActiveRecord::Base.stub(:configurations, @configurations) do
-          # To refrain from connecting to a newly created empty DB in
-          # sqlite3_mem tests
-          ActiveRecord::Base.connection_handler.stub(
-            :establish_connection,
-            nil
-          ) do
-            yield
-          end
-        end
-      end
   end
 
   class DatabaseTasksCreateCurrentTest < ActiveRecord::TestCase
     def setup
+      @old_configurations = ActiveRecord::Base.configurations
+
       @configurations = {
         "development" => { "database" => "dev-db" },
         "test"        => { "database" => "test-db" },
-        "production"  => { "url" => "prod-db-url" }
+        "production"  => { "url" => "abstract://prod-db-url" }
       }
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      ActiveRecord::Base.configurations = @old_configurations
     end
 
     def test_creates_current_environment_database
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :create,
@@ -267,7 +264,7 @@ module ActiveRecord
     end
 
     def test_creates_current_environment_database_with_url
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :create,
@@ -281,7 +278,7 @@ module ActiveRecord
     end
 
     def test_creates_test_and_development_databases_when_env_was_not_specified
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :create,
@@ -301,7 +298,7 @@ module ActiveRecord
       old_env = ENV["RAILS_ENV"]
       ENV["RAILS_ENV"] = "development"
 
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :create,
@@ -328,29 +325,27 @@ module ActiveRecord
         end
       end
     end
-
-    private
-
-      def with_stubbed_configurations_establish_connection
-        ActiveRecord::Base.stub(:configurations, @configurations) do
-          ActiveRecord::Base.stub(:establish_connection, nil) do
-            yield
-          end
-        end
-      end
   end
 
   class DatabaseTasksCreateCurrentThreeTierTest < ActiveRecord::TestCase
     def setup
+      @old_configurations = ActiveRecord::Base.configurations
+
       @configurations = {
         "development" => { "primary" => { "database" => "dev-db" }, "secondary" => { "database" => "secondary-dev-db" } },
         "test" => { "primary" => { "database" => "test-db" }, "secondary" => { "database" => "secondary-test-db" } },
-        "production" => { "primary" => { "url" => "prod-db-url" }, "secondary" => { "url" => "secondary-prod-db-url" } }
+        "production" => { "primary" => { "url" => "abstract://prod-db-url" }, "secondary" => { "url" => "abstract://secondary-prod-db-url" } }
       }
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      ActiveRecord::Base.configurations = @old_configurations
     end
 
     def test_creates_current_environment_database
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :create,
@@ -367,7 +362,7 @@ module ActiveRecord
     end
 
     def test_creates_current_environment_database_with_url
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :create,
@@ -384,7 +379,7 @@ module ActiveRecord
     end
 
     def test_creates_test_and_development_databases_when_env_was_not_specified
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :create,
@@ -406,7 +401,7 @@ module ActiveRecord
       old_env = ENV["RAILS_ENV"]
       ENV["RAILS_ENV"] = "development"
 
-      with_stubbed_configurations_establish_connection do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :create,
@@ -439,16 +434,6 @@ module ActiveRecord
         end
       end
     end
-
-    private
-
-      def with_stubbed_configurations_establish_connection
-        ActiveRecord::Base.stub(:configurations, @configurations) do
-          ActiveRecord::Base.stub(:establish_connection, nil) do
-            yield
-          end
-        end
-      end
   end
 
   class DatabaseTasksDropTest < ActiveRecord::TestCase
@@ -467,20 +452,24 @@ module ActiveRecord
 
   class DatabaseTasksDropAllTest < ActiveRecord::TestCase
     def setup
+      @old_configurations = ActiveRecord::Base.configurations
       @configurations = { development: { "database" => "my-db" } }
 
       $stdout, @original_stdout = StringIO.new, $stdout
       $stderr, @original_stderr = StringIO.new, $stderr
+
+      ActiveRecord::Base.configurations = @configurations
     end
 
     def teardown
       $stdout, $stderr = @original_stdout, @original_stderr
+      ActiveRecord::Base.configurations = @old_configurations
     end
 
     def test_ignores_configurations_without_databases
       @configurations[:development]["database"] = nil
 
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
           ActiveRecord::Tasks::DatabaseTasks.drop_all
         end
@@ -490,7 +479,7 @@ module ActiveRecord
     def test_ignores_remote_databases
       @configurations[:development]["host"] = "my.server.tld"
 
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
           ActiveRecord::Tasks::DatabaseTasks.drop_all
         end
@@ -500,7 +489,7 @@ module ActiveRecord
     def test_warning_for_remote_databases
       @configurations[:development]["host"] = "my.server.tld"
 
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         ActiveRecord::Tasks::DatabaseTasks.drop_all
 
         assert_match "This task only modifies local databases. my-db is on a remote host.",
@@ -511,7 +500,7 @@ module ActiveRecord
     def test_drops_configurations_with_local_ip
       @configurations[:development]["host"] = "127.0.0.1"
 
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
           ActiveRecord::Tasks::DatabaseTasks.drop_all
         end
@@ -521,7 +510,7 @@ module ActiveRecord
     def test_drops_configurations_with_local_host
       @configurations[:development]["host"] = "localhost"
 
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
           ActiveRecord::Tasks::DatabaseTasks.drop_all
         end
@@ -531,7 +520,7 @@ module ActiveRecord
     def test_drops_configurations_with_blank_hosts
       @configurations[:development]["host"] = nil
 
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
           ActiveRecord::Tasks::DatabaseTasks.drop_all
         end
@@ -541,15 +530,22 @@ module ActiveRecord
 
   class DatabaseTasksDropCurrentTest < ActiveRecord::TestCase
     def setup
+      @old_configurations = ActiveRecord::Base.configurations
       @configurations = {
         "development" => { "database" => "dev-db" },
         "test"        => { "database" => "test-db" },
-        "production"  => { "url" => "prod-db-url" }
+        "production"  => { "url" => "abstract://prod-db-url" }
       }
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      ActiveRecord::Base.configurations = @old_configurations
     end
 
     def test_drops_current_environment_database
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called_with(ActiveRecord::Tasks::DatabaseTasks, :drop,
           ["database" => "test-db"]) do
           ActiveRecord::Tasks::DatabaseTasks.drop_current(
@@ -560,7 +556,7 @@ module ActiveRecord
     end
 
     def test_drops_current_environment_database_with_url
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called_with(ActiveRecord::Tasks::DatabaseTasks, :drop,
           ["url" => "prod-db-url"]) do
           ActiveRecord::Tasks::DatabaseTasks.drop_current(
@@ -571,7 +567,7 @@ module ActiveRecord
     end
 
     def test_drops_test_and_development_databases_when_env_was_not_specified
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :drop,
@@ -591,7 +587,7 @@ module ActiveRecord
       old_env = ENV["RAILS_ENV"]
       ENV["RAILS_ENV"] = "development"
 
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :drop,
@@ -612,15 +608,22 @@ module ActiveRecord
 
   class DatabaseTasksDropCurrentThreeTierTest < ActiveRecord::TestCase
     def setup
+      @old_configurations = ActiveRecord::Base.configurations
       @configurations = {
         "development" => { "primary" => { "database" => "dev-db" }, "secondary" => { "database" => "secondary-dev-db" } },
         "test" => { "primary" => { "database" => "test-db" }, "secondary" => { "database" => "secondary-test-db" } },
-        "production" => { "primary" => { "url" => "prod-db-url" }, "secondary" => { "url" => "secondary-prod-db-url" } }
+        "production" => { "primary" => { "url" => "abstract://prod-db-url" }, "secondary" => { "url" => "abstract://secondary-prod-db-url" } }
       }
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      ActiveRecord::Base.configurations = @old_configurations
     end
 
     def test_drops_current_environment_database
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :drop,
@@ -637,7 +640,7 @@ module ActiveRecord
     end
 
     def test_drops_current_environment_database_with_url
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :drop,
@@ -654,7 +657,7 @@ module ActiveRecord
     end
 
     def test_drops_test_and_development_databases_when_env_was_not_specified
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :drop,
@@ -676,7 +679,7 @@ module ActiveRecord
       old_env = ENV["RAILS_ENV"]
       ENV["RAILS_ENV"] = "development"
 
-      ActiveRecord::Base.stub(:configurations, @configurations) do
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :drop,
@@ -848,12 +851,16 @@ module ActiveRecord
 
   class DatabaseTasksPurgeCurrentTest < ActiveRecord::TestCase
     def test_purges_current_environment_database
+      old_configurations = ActiveRecord::Base.configurations
       configurations = {
         "development" => { "database" => "dev-db" },
         "test"        => { "database" => "test-db" },
         "production"  => { "database" => "prod-db" }
       }
-      ActiveRecord::Base.stub(:configurations, configurations) do
+
+      ActiveRecord::Base.configurations = configurations
+
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :purge,
@@ -864,13 +871,17 @@ module ActiveRecord
           end
         end
       end
+    ensure
+      ActiveRecord::Base.configurations = old_configurations
     end
   end
 
   class DatabaseTasksPurgeAllTest < ActiveRecord::TestCase
     def test_purge_all_local_configurations
+      old_configurations = ActiveRecord::Base.configurations
       configurations = { development: { "database" => "my-db" } }
-      ActiveRecord::Base.stub(:configurations, configurations) do
+      ActiveRecord::Base.configurations = configurations
+      ActiveRecord::Base.configurations do
         assert_called_with(
           ActiveRecord::Tasks::DatabaseTasks,
           :purge,
@@ -879,6 +890,8 @@ module ActiveRecord
           ActiveRecord::Tasks::DatabaseTasks.purge_all
         end
       end
+    ensure
+      ActiveRecord::Base.configurations = old_configurations
     end
   end
 
diff --git a/activerecord/test/cases/tasks/legacy_database_tasks_test.rb b/activerecord/test/cases/tasks/legacy_database_tasks_test.rb
new file mode 100644
index 0000000000..ffa55be878
--- /dev/null
+++ b/activerecord/test/cases/tasks/legacy_database_tasks_test.rb
@@ -0,0 +1,591 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "active_record/tasks/database_tasks"
+
+module ActiveRecord
+  class LegacyDatabaseTasksCreateAllTest < ActiveRecord::TestCase
+    def setup
+      @old_configurations = ActiveRecord::Base.configurations.to_h
+
+      @configurations = { "development" => { "database" => "my-db" } }
+
+      $stdout, @original_stdout = StringIO.new, $stdout
+      $stderr, @original_stderr = StringIO.new, $stderr
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      $stdout, $stderr = @original_stdout, @original_stderr
+      ActiveRecord::Base.configurations = @old_configurations
+    end
+
+    def test_ignores_configurations_without_databases
+      @configurations["development"]["database"] = nil
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+          ActiveRecord::Tasks::DatabaseTasks.create_all
+        end
+      end
+    end
+
+    def test_ignores_remote_databases
+      @configurations["development"]["host"] = "my.server.tld"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+          ActiveRecord::Tasks::DatabaseTasks.create_all
+        end
+      end
+    end
+
+    def test_warning_for_remote_databases
+      @configurations["development"]["host"] = "my.server.tld"
+
+      ActiveRecord::Base.configurations.to_h do
+        ActiveRecord::Tasks::DatabaseTasks.create_all
+
+        assert_match "This task only modifies local databases. my-db is on a remote host.",
+          $stderr.string
+      end
+    end
+
+    def test_creates_configurations_with_local_ip
+      @configurations["development"]["host"] = "127.0.0.1"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+          ActiveRecord::Tasks::DatabaseTasks.create_all
+        end
+      end
+    end
+
+    def test_creates_configurations_with_local_host
+      @configurations["development"]["host"] = "localhost"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+          ActiveRecord::Tasks::DatabaseTasks.create_all
+        end
+      end
+    end
+
+    def test_creates_configurations_with_blank_hosts
+      @configurations["development"]["host"] = nil
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+          ActiveRecord::Tasks::DatabaseTasks.create_all
+        end
+      end
+    end
+  end
+
+  class LegacyDatabaseTasksCreateCurrentTest < ActiveRecord::TestCase
+    def setup
+      @old_configurations = ActiveRecord::Base.configurations.to_h
+
+      @configurations = {
+        "development" => { "database" => "dev-db" },
+        "test"        => { "database" => "test-db" },
+        "production"  => { "url" => "abstract://prod-db-url" }
+      }
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      ActiveRecord::Base.configurations = @old_configurations
+    end
+
+    def test_creates_current_environment_database
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :create,
+          ["database" => "test-db"],
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.create_current(
+            ActiveSupport::StringInquirer.new("test")
+          )
+        end
+      end
+    end
+
+    def test_creates_current_environment_database_with_url
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :create,
+          ["url" => "prod-db-url"],
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.create_current(
+            ActiveSupport::StringInquirer.new("production")
+          )
+        end
+      end
+    end
+
+    def test_creates_test_and_development_databases_when_env_was_not_specified
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :create,
+          [
+            ["database" => "dev-db"],
+            ["database" => "test-db"]
+          ],
+        ) do
+            ActiveRecord::Tasks::DatabaseTasks.create_current(
+              ActiveSupport::StringInquirer.new("development")
+            )
+          end
+      end
+    end
+
+    def test_creates_test_and_development_databases_when_rails_env_is_development
+      old_env = ENV["RAILS_ENV"]
+      ENV["RAILS_ENV"] = "development"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :create,
+          [
+            ["database" => "dev-db"],
+            ["database" => "test-db"]
+          ],
+        ) do
+            ActiveRecord::Tasks::DatabaseTasks.create_current(
+              ActiveSupport::StringInquirer.new("development")
+            )
+          end
+      end
+    ensure
+      ENV["RAILS_ENV"] = old_env
+    end
+
+    def test_establishes_connection_for_the_given_environments
+      ActiveRecord::Tasks::DatabaseTasks.stub(:create, nil) do
+        assert_called_with(ActiveRecord::Base, :establish_connection, [:development]) do
+          ActiveRecord::Tasks::DatabaseTasks.create_current(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    end
+  end
+
+  class LegacyDatabaseTasksCreateCurrentThreeTierTest < ActiveRecord::TestCase
+    def setup
+      @old_configurations = ActiveRecord::Base.configurations.to_h
+
+      @configurations = {
+        "development" => { "primary" => { "database" => "dev-db" }, "secondary" => { "database" => "secondary-dev-db" } },
+        "test" => { "primary" => { "database" => "test-db" }, "secondary" => { "database" => "secondary-test-db" } },
+        "production" => { "primary" => { "url" => "abstract://prod-db-url" }, "secondary" => { "url" => "abstract://secondary-prod-db-url" } }
+      }
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      ActiveRecord::Base.configurations = @old_configurations
+    end
+
+    def test_creates_current_environment_database
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :create,
+          [
+            ["database" => "test-db"],
+            ["database" => "secondary-test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.create_current(
+            ActiveSupport::StringInquirer.new("test")
+          )
+        end
+      end
+    end
+
+    def test_creates_current_environment_database_with_url
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :create,
+          [
+            ["url" => "prod-db-url"],
+            ["url" => "secondary-prod-db-url"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.create_current(
+            ActiveSupport::StringInquirer.new("production")
+          )
+        end
+      end
+    end
+
+    def test_creates_test_and_development_databases_when_env_was_not_specified
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :create,
+          [
+            ["database" => "dev-db"],
+            ["database" => "secondary-dev-db"],
+            ["database" => "test-db"],
+            ["database" => "secondary-test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.create_current(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    end
+
+    def test_creates_test_and_development_databases_when_rails_env_is_development
+      old_env = ENV["RAILS_ENV"]
+      ENV["RAILS_ENV"] = "development"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :create,
+          [
+            ["database" => "dev-db"],
+            ["database" => "secondary-dev-db"],
+            ["database" => "test-db"],
+            ["database" => "secondary-test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.create_current(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    ensure
+      ENV["RAILS_ENV"] = old_env
+    end
+
+    def test_establishes_connection_for_the_given_environments_config
+      ActiveRecord::Tasks::DatabaseTasks.stub(:create, nil) do
+        assert_called_with(
+          ActiveRecord::Base,
+          :establish_connection,
+          [:development]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.create_current(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    end
+  end
+
+  class LegacyDatabaseTasksDropAllTest < ActiveRecord::TestCase
+    def setup
+      @old_configurations = ActiveRecord::Base.configurations.to_h
+
+      @configurations = { development: { "database" => "my-db" } }
+
+      $stdout, @original_stdout = StringIO.new, $stdout
+      $stderr, @original_stderr = StringIO.new, $stderr
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      $stdout, $stderr = @original_stdout, @original_stderr
+      ActiveRecord::Base.configurations = @old_configurations
+    end
+
+    def test_ignores_configurations_without_databases
+      @configurations[:development]["database"] = nil
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_all
+        end
+      end
+    end
+
+    def test_ignores_remote_databases
+      @configurations[:development]["host"] = "my.server.tld"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_all
+        end
+      end
+    end
+
+    def test_warning_for_remote_databases
+      @configurations[:development]["host"] = "my.server.tld"
+
+      ActiveRecord::Base.configurations.to_h do
+        ActiveRecord::Tasks::DatabaseTasks.drop_all
+
+        assert_match "This task only modifies local databases. my-db is on a remote host.",
+          $stderr.string
+      end
+    end
+
+    def test_drops_configurations_with_local_ip
+      @configurations[:development]["host"] = "127.0.0.1"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_all
+        end
+      end
+    end
+
+    def test_drops_configurations_with_local_host
+      @configurations[:development]["host"] = "localhost"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_all
+        end
+      end
+    end
+
+    def test_drops_configurations_with_blank_hosts
+      @configurations[:development]["host"] = nil
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_all
+        end
+      end
+    end
+  end
+
+  class LegacyDatabaseTasksDropCurrentTest < ActiveRecord::TestCase
+    def setup
+      @old_configurations = ActiveRecord::Base.configurations.to_h
+
+      @configurations = {
+        "development" => { "database" => "dev-db" },
+        "test"        => { "database" => "test-db" },
+        "production"  => { "url" => "abstract://prod-db-url" }
+      }
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      ActiveRecord::Base.configurations = @old_configurations
+    end
+
+    def test_drops_current_environment_database
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(ActiveRecord::Tasks::DatabaseTasks, :drop,
+                           ["database" => "test-db"]) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_current(
+            ActiveSupport::StringInquirer.new("test")
+          )
+        end
+      end
+    end
+
+    def test_drops_current_environment_database_with_url
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(ActiveRecord::Tasks::DatabaseTasks, :drop,
+                           ["url" => "prod-db-url"]) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_current(
+            ActiveSupport::StringInquirer.new("production")
+          )
+        end
+      end
+    end
+
+    def test_drops_test_and_development_databases_when_env_was_not_specified
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :drop,
+          [
+            ["database" => "dev-db"],
+            ["database" => "test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_current(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    end
+
+    def test_drops_testand_development_databases_when_rails_env_is_development
+      old_env = ENV["RAILS_ENV"]
+      ENV["RAILS_ENV"] = "development"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :drop,
+          [
+            ["database" => "dev-db"],
+            ["database" => "test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_current(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    ensure
+      ENV["RAILS_ENV"] = old_env
+    end
+  end
+
+  class LegacyDatabaseTasksDropCurrentThreeTierTest < ActiveRecord::TestCase
+    def setup
+      @old_configurations = ActiveRecord::Base.configurations.to_h
+
+      @configurations = {
+        "development" => { "primary" => { "database" => "dev-db" }, "secondary" => { "database" => "secondary-dev-db" } },
+        "test" => { "primary" => { "database" => "test-db" }, "secondary" => { "database" => "secondary-test-db" } },
+        "production" => { "primary" => { "url" => "abstract://prod-db-url" }, "secondary" => { "url" => "abstract://secondary-prod-db-url" } }
+      }
+
+      ActiveRecord::Base.configurations = @configurations
+    end
+
+    def teardown
+      ActiveRecord::Base.configurations = @old_configurations
+    end
+
+    def test_drops_current_environment_database
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :drop,
+          [
+            ["database" => "test-db"],
+            ["database" => "secondary-test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_current(
+            ActiveSupport::StringInquirer.new("test")
+          )
+        end
+      end
+    end
+
+    def test_drops_current_environment_database_with_url
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :drop,
+          [
+            ["url" => "prod-db-url"],
+            ["url" => "secondary-prod-db-url"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_current(
+            ActiveSupport::StringInquirer.new("production")
+          )
+        end
+      end
+    end
+
+    def test_drops_test_and_development_databases_when_env_was_not_specified
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :drop,
+          [
+            ["database" => "dev-db"],
+            ["database" => "secondary-dev-db"],
+            ["database" => "test-db"],
+            ["database" => "secondary-test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_current(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    end
+
+    def test_drops_testand_development_databases_when_rails_env_is_development
+      old_env = ENV["RAILS_ENV"]
+      ENV["RAILS_ENV"] = "development"
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :drop,
+          [
+            ["database" => "dev-db"],
+            ["database" => "secondary-dev-db"],
+            ["database" => "test-db"],
+            ["database" => "secondary-test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.drop_current(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    ensure
+      ENV["RAILS_ENV"] = old_env
+    end
+  end
+
+  class LegacyDatabaseTasksPurgeCurrentTest < ActiveRecord::TestCase
+    def test_purges_current_environment_database
+      @old_configurations = ActiveRecord::Base.configurations.to_h
+
+      configurations = {
+        "development" => { "database" => "dev-db" },
+        "test"        => { "database" => "test-db" },
+        "production"  => { "database" => "prod-db" }
+      }
+
+      ActiveRecord::Base.configurations = configurations
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :purge,
+          ["database" => "prod-db"]
+        ) do
+          assert_called_with(ActiveRecord::Base, :establish_connection, [:production]) do
+            ActiveRecord::Tasks::DatabaseTasks.purge_current("production")
+          end
+        end
+      end
+    ensure
+      ActiveRecord::Base.configurations = @old_configurations
+    end
+  end
+
+  class LegacyDatabaseTasksPurgeAllTest < ActiveRecord::TestCase
+    def test_purge_all_local_configurations
+      @old_configurations = ActiveRecord::Base.configurations.to_h
+
+      configurations = { development: { "database" => "my-db" } }
+      ActiveRecord::Base.configurations = configurations
+
+      ActiveRecord::Base.configurations.to_h do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :purge,
+          ["database" => "my-db"]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.purge_all
+        end
+      end
+    ensure
+      ActiveRecord::Base.configurations = @old_configurations
+    end
+  end
+end