test local time serialization

spec/datadog/di/serializer_helper.rb

@@ -2,7 +2,6 @@ module SerializerHelper
   def define_serialize_value_cases(cases)
     cases.each do |c|
       value = c.fetch(:input)
-      expected = c.fetch(:expected)
       var_name = c[:var_name]
 
       context c.fetch(:name) do
@@ -18,8 +17,15 @@ def define_serialize_value_cases(cases)
           {name: var_name}
         end
 
-        it "serializes as expected" do
-          expect(serialized).to eq(expected)
+        if expected_matches = c[:expected_matches]
+          it "serialization matches expectation" do
+            expect(serialized).to match(expected_matches)
+          end
+        else
+          expected = c.fetch(:expected)
+          it "serializes exactly as specified" do
+            expect(serialized).to eq(expected)
+          end
         end
       end
     end

spec/datadog/di/serializer_spec.rb

@@ -65,8 +65,12 @@ class DISerializerCustomExceptionTestClass; end
        expected: {type: "String", notCapturedReason: "redactedIdent"}},
       {name: "variable name given and is not a redacted identifier", input: "123", var_name: "normal",
        expected: {type: "String", value: "123"}},
-      {name: 'Time value', input: Time.utc(2020, 1, 2, 3, 4, 5),
+      # We can assert exact value when the time zone is UTC,
+      # since we don't know the local time zone ahead of time.
+      {name: 'Time value in UTC', input: Time.utc(2020, 1, 2, 3, 4, 5),
         expected: {type: 'Time', value: '2020-01-02T03:04:05Z'}},
+      {name: 'Time value in local time zone', input: Time.local(2020, 1, 2, 3, 4, 5),
+        expected_matches: {type: 'Time', value: %r,\A2020-01-02T03:04:05[-+]\d\d:\d\d\z, }},
       {name: 'Date value', input: Date.new(2020, 1, 2),
         expected: {type: 'Date', value: '2020-01-02'}},
       {name: 'DateTime value', input: DateTime.new(2020, 1, 2, 3, 4, 5),