Test that no datetime precision isn't truncated on assignment

Also, max precision (= 6) isn't regarded as unlimited precision for now.

1 files changed, 21 insertions, 1 deletions

diff --git a/activerecord/test/cases/date_time_precision_test.rb b/activerecord/test/cases/date_time_precision_test.rb
index e64a8372d0..9d1af9362d 100644
--- a/activerecord/test/cases/date_time_precision_test.rb
+++ b/activerecord/test/cases/date_time_precision_test.rb
@@ -29,7 +29,7 @@ if subsecond_precision_supported?
 
     def test_datetime_precision_is_truncated_on_assignment
       @connection.create_table(:foos, force: true)
-      @connection.add_column :foos, :created_at,  :datetime, precision: 0
+      @connection.add_column :foos, :created_at, :datetime, precision: 0
       @connection.add_column :foos, :updated_at, :datetime, precision: 6
 
       time = ::Time.now.change(nsec: 123456789)
@@ -45,6 +45,26 @@ if subsecond_precision_supported?
       assert_equal 123456000, foo.updated_at.nsec
     end
 
+    unless current_adapter?(:Mysql2Adapter)
+      def test_no_datetime_precision_isnt_truncated_on_assignment
+        @connection.create_table(:foos, force: true)
+        @connection.add_column :foos, :created_at, :datetime
+        @connection.add_column :foos, :updated_at, :datetime, precision: 6
+
+        time = ::Time.now.change(nsec: 123)
+        foo = Foo.new(created_at: time, updated_at: time)
+
+        assert_equal 123, foo.created_at.nsec
+        assert_equal 0, foo.updated_at.nsec
+
+        foo.save!
+        foo.reload
+
+        assert_equal 0, foo.created_at.nsec
+        assert_equal 0, foo.updated_at.nsec
+      end
+    end
+
     def test_timestamps_helper_with_custom_precision
       @connection.create_table(:foos, force: true) do |t|
         t.timestamps precision: 4