Merge pull request #15857 from zuhao/refactor_activesupport_encoding_test

Avoid hardcoded magic number in test teardown.

activesupport/test/json/encoding_test.rb

@@ -494,31 +494,28 @@ def test_twz_to_json_with_use_standard_json_time_format_config_set_to_true
 
   def test_twz_to_json_with_custom_time_precision
     with_standard_json_time_format(true) do
-      ActiveSupport::JSON::Encoding.time_precision = 0
+      with_time_precision(0) do
         zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
         time = ActiveSupport::TimeWithZone.new(Time.utc(2000), zone)
         assert_equal "\"1999-12-31T19:00:00-05:00\"", ActiveSupport::JSON.encode(time)
       end
-  ensure
-    ActiveSupport::JSON::Encoding.time_precision = 3
+    end
   end
 
   def test_time_to_json_with_custom_time_precision
     with_standard_json_time_format(true) do
-      ActiveSupport::JSON::Encoding.time_precision = 0
+      with_time_precision(0) do
         assert_equal "\"2000-01-01T00:00:00Z\"", ActiveSupport::JSON.encode(Time.utc(2000))
       end
-  ensure
-    ActiveSupport::JSON::Encoding.time_precision = 3
+    end
   end
 
   def test_datetime_to_json_with_custom_time_precision
     with_standard_json_time_format(true) do
-      ActiveSupport::JSON::Encoding.time_precision = 0
+      with_time_precision(0) do
         assert_equal "\"2000-01-01T00:00:00+00:00\"", ActiveSupport::JSON.encode(DateTime.new(2000))
       end
-  ensure
-    ActiveSupport::JSON::Encoding.time_precision = 3
+    end
   end
 
   def test_twz_to_json_when_wrapping_a_date_time
@@ -539,4 +536,12 @@ def with_standard_json_time_format(boolean = true)
     ensure
       ActiveSupport.use_standard_json_time_format = old
     end
+
+    def with_time_precision(value)
+      old_value = ActiveSupport::JSON::Encoding.time_precision
+      ActiveSupport::JSON::Encoding.time_precision = value
+      yield
+    ensure
+      ActiveSupport::JSON::Encoding.time_precision = old_value
+    end
 end