1 files changed, 22 insertions, 7 deletions
diff --git a/activesupport/test/core_ext/time_with_zone_test.rb b/activesupport/test/core_ext/time_with_zone_test.rb
index 43fe572bfc..4ea8d2bed6 100644
--- a/activesupport/test/core_ext/time_with_zone_test.rb
+++ b/activesupport/test/core_ext/time_with_zone_test.rb
@@ -67,17 +67,25 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_to_json_with_use_standard_json_time_format_config_set_to_false
-    old, ActiveSupport.use_standard_json_time_format = ActiveSupport.use_standard_json_time_format, false
-    assert_equal "\"1999/12/31 19:00:00 -0500\"", ActiveSupport::JSON.encode(@twz)
-  ensure
-    ActiveSupport.use_standard_json_time_format = old
+    with_standard_json_time_format(false) do
+      assert_equal "\"1999/12/31 19:00:00 -0500\"", ActiveSupport::JSON.encode(@twz)
+    end
   end
 
   def test_to_json_with_use_standard_json_time_format_config_set_to_true
-    old, ActiveSupport.use_standard_json_time_format = ActiveSupport.use_standard_json_time_format, true
-    assert_equal "\"1999-12-31T19:00:00.000-05:00\"", ActiveSupport::JSON.encode(@twz)
+    with_standard_json_time_format(true) do
+      assert_equal "\"1999-12-31T19:00:00.000-05:00\"", ActiveSupport::JSON.encode(@twz)
+    end
+  end
+
+  def test_to_json_with_custom_subsecond_resolution
+    with_standard_json_time_format(true) do
+      ActiveSupport::JSON::Encoding.subsecond_fraction_digits = 0
+
+      assert_equal "\"1999-12-31T19:00:00-05:00\"", ActiveSupport::JSON.encode(@twz)
+    end
   ensure
-    ActiveSupport.use_standard_json_time_format = old
+    ActiveSupport::JSON::Encoding.subsecond_fraction_digits = nil
   end
 
   def test_to_json_when_wrapping_a_date_time
@@ -814,6 +822,13 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     ensure
       old_tz ? ENV['TZ'] = old_tz : ENV.delete('TZ')
     end
+
+    def with_standard_json_time_format(boolean = true)
+      old, ActiveSupport.use_standard_json_time_format = ActiveSupport.use_standard_json_time_format, boolean
+      yield
+    ensure
+      ActiveSupport.use_standard_json_time_format = old
+    end
 end
 
 class TimeWithZoneMethodsForTimeAndDateTimeTest < ActiveSupport::TestCase