diff --git a/activemodel/test/cases/attributes_test.rb b/activemodel/test/cases/attributes_test.rb
index 6ff5af09206..387005f56c4 100644
--- a/activemodel/test/cases/attributes_test.rb
+++ b/activemodel/test/cases/attributes_test.rb
@@ -142,5 +142,11 @@ module ActiveModel
       data.freeze
       assert_nothing_raised { data.freeze }
     end
+
+    test "unknown type error is raised" do
+      assert_raise(ArgumentError) do
+        ModelForAttributesTest.attribute :foo, :unknown
+      end
+    end
   end
 end
diff --git a/activerecord/lib/active_record/attributes.rb b/activerecord/lib/active_record/attributes.rb
index 04a83d5dc4d..9e803fa58e9 100644
--- a/activerecord/lib/active_record/attributes.rb
+++ b/activerecord/lib/active_record/attributes.rb
@@ -214,8 +214,7 @@ module ActiveRecord
 
         case cast_type
         when Symbol
-          type = cast_type
-          cast_type = -> _ { Type.lookup(type, **options, adapter: Type.adapter_name_from(self)) }
+          cast_type = Type.lookup(cast_type, **options, adapter: Type.adapter_name_from(self))
         when nil
           if (prev_cast_type, prev_default = attributes_to_define_after_schema_loads[name])
             default = prev_default if default == NO_DEFAULT_PROVIDED
diff --git a/activerecord/test/cases/adapters/postgresql/datatype_test.rb b/activerecord/test/cases/adapters/postgresql/datatype_test.rb
index 2cfa35760df..ff9ac166a6f 100644
--- a/activerecord/test/cases/adapters/postgresql/datatype_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/datatype_test.rb
@@ -7,7 +7,7 @@ class PostgresqlTime < ActiveRecord::Base
   # Declare attributes to get rid from deprecation warnings on ActiveRecord 6.1
   attribute :time_interval,        :string
   attribute :scaled_time_interval, :interval
-end
+end if current_adapter?(:PostgreSQLAdapter)
 
 class PostgresqlOid < ActiveRecord::Base
 end
diff --git a/activerecord/test/cases/adapters/postgresql/geometric_test.rb b/activerecord/test/cases/adapters/postgresql/geometric_test.rb
index f312b6e23d7..1e4f741f5fe 100644
--- a/activerecord/test/cases/adapters/postgresql/geometric_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/geometric_test.rb
@@ -16,7 +16,7 @@ class PostgresqlPointTest < ActiveRecord::PostgreSQLTestCase
     attribute :legacy_x, :legacy_point
     attribute :legacy_y, :legacy_point
     attribute :legacy_z, :legacy_point
-  end
+  end if current_adapter?(:PostgreSQLAdapter)
 
   def setup
     @connection = ActiveRecord::Base.connection
diff --git a/activerecord/test/cases/adapters/postgresql/interval_test.rb b/activerecord/test/cases/adapters/postgresql/interval_test.rb
index 81f4e87181f..ca1fe4bc765 100644
--- a/activerecord/test/cases/adapters/postgresql/interval_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/interval_test.rb
@@ -12,7 +12,7 @@ class PostgresqlIntervalTest < ActiveRecord::PostgreSQLTestCase
     attribute :default_term, :interval
     attribute :all_terms,    :interval, array: true
     attribute :legacy_term,  :string
-  end
+  end if current_adapter?(:PostgreSQLAdapter)
 
   class DeprecatedIntervalDataType < ActiveRecord::Base; end
 
diff --git a/activerecord/test/cases/attributes_test.rb b/activerecord/test/cases/attributes_test.rb
index 652d09ae9fa..efecf602f8b 100644
--- a/activerecord/test/cases/attributes_test.rb
+++ b/activerecord/test/cases/attributes_test.rb
@@ -348,6 +348,12 @@ module ActiveRecord
       assert_equal "foo", klass.new(no_type: "foo").no_type
     end
 
+    test "unknown type error is raised" do
+      assert_raise(ArgumentError) do
+        OverloadedType.attribute :foo, :unknown
+      end
+    end
+
     test "immutable_strings_by_default changes schema inference for string columns" do
       with_immutable_strings do
         OverloadedType.reset_column_information
diff --git a/activerecord/test/cases/inheritance_test.rb b/activerecord/test/cases/inheritance_test.rb
index b316e6a6374..1a8ee5fcc62 100644
--- a/activerecord/test/cases/inheritance_test.rb
+++ b/activerecord/test/cases/inheritance_test.rb
@@ -597,17 +597,10 @@ end
 
 class InheritanceAttributeMappingTest < ActiveRecord::TestCase
   setup do
-    @old_registry = ActiveRecord::Type.registry
-    ActiveRecord::Type.registry = ActiveRecord::Type.registry.dup
-    ActiveRecord::Type.register :omg_sti, InheritanceAttributeMappingTest::OmgStiType
     Company.delete_all
     Sponsor.delete_all
   end
 
-  teardown do
-    ActiveRecord::Type.registry = @old_registry
-  end
-
   class OmgStiType < ActiveRecord::Type::String
     def cast_value(value)
       if value =~ /\Aomg_(.+)\z/
@@ -624,6 +617,8 @@ class InheritanceAttributeMappingTest < ActiveRecord::TestCase
     end
   end
 
+  ActiveRecord::Type.register :omg_sti, OmgStiType
+
   class Company < ActiveRecord::Base
     self.table_name = "companies"
     attribute :type, :omg_sti