3 files changed, 34 insertions, 5 deletions
diff --git a/activesupport/test/json/decoding_test.rb b/activesupport/test/json/decoding_test.rb
index 6d1d8f1b95..6f5051c312 100644
--- a/activesupport/test/json/decoding_test.rb
+++ b/activesupport/test/json/decoding_test.rb
@@ -75,12 +75,17 @@ class TestJSONDecoding < ActiveSupport::TestCase
   }
 
   TESTS.each_with_index do |(json, expected), index|
+    fail_message = "JSON decoding failed for #{json}"
+
     test "json decodes #{index}" do
       with_tz_default "Eastern Time (US & Canada)" do
         with_parse_json_times(true) do
           silence_warnings do
-            assert_equal expected, ActiveSupport::JSON.decode(json), "JSON decoding \
-            failed for #{json}"
+            if expected.nil?
+              assert_nil ActiveSupport::JSON.decode(json), fail_message
+            else
+              assert_equal expected, ActiveSupport::JSON.decode(json), fail_message
+            end
           end
         end
       end
diff --git a/activesupport/test/json/encoding_test.rb b/activesupport/test/json/encoding_test.rb
index fc3af02cbc..6d8f7cfbd0 100644
--- a/activesupport/test/json/encoding_test.rb
+++ b/activesupport/test/json/encoding_test.rb
@@ -329,7 +329,7 @@ class TestJSONEncoding < ActiveSupport::TestCase
   end
 
   def test_nil_true_and_false_represented_as_themselves
-    assert_equal nil,   nil.as_json
+    assert_nil nil.as_json
     assert_equal true,  true.as_json
     assert_equal false, false.as_json
   end
@@ -432,7 +432,27 @@ EXPECTED
     assert_equal '"foo"', ActiveSupport::JSON.encode(exception)
   end
 
-  protected
+  class InfiniteNumber
+    def as_json(options = nil)
+      { "number" => Float::INFINITY }
+    end
+  end
+
+  def test_to_json_works_when_as_json_returns_infinite_number
+    assert_equal '{"number":null}', InfiniteNumber.new.to_json
+  end
+
+  class NaNNumber
+    def as_json(options = nil)
+      { "number" => Float::NAN }
+    end
+  end
+
+  def test_to_json_works_when_as_json_returns_NaN_number
+    assert_equal '{"number":null}', NaNNumber.new.to_json
+  end
+
+  private
 
     def object_keys(json_object)
       json_object[1..-2].scan(/([^{}:,\s]+):/).flatten.sort
diff --git a/activesupport/test/json/encoding_test_cases.rb b/activesupport/test/json/encoding_test_cases.rb
index 8eac246937..7e4775cec8 100644
--- a/activesupport/test/json/encoding_test_cases.rb
+++ b/activesupport/test/json/encoding_test_cases.rb
@@ -1,4 +1,8 @@
 require "bigdecimal"
+require "date"
+require "time"
+require "pathname"
+require "uri"
 
 module JSONTest
   class Foo
@@ -23,7 +27,7 @@ module JSONTest
     end
   end
 
-  class MyStruct < Struct.new(:name, :value)
+  MyStruct = Struct.new(:name, :value) do
     def initialize(*)
       @unused = "unused instance variable"
       super