fixes for caching test on jruby

diff --git a/test/caching_test.rb b/test/caching_test.rb
index 4ccef91..c6d9808 100644
--- a/test/caching_test.rb
+++ b/test/caching_test.rb
@@ -1,4 +1,5 @@
 require File.expand_path('../support/test_helper', __FILE__)
+require 'tempfile'

 class CachingTestTest < Minitest::Test
   def setup
@@ -6,8 +7,10 @@ class CachingTestTest < Minitest::Test
   end

   def teardown
-    @schema.close
-    @schema.unlink
+    if @Schema
+      @schema.close
+      @schema.unlink
+    end

     JSON::Validator.clear_cache
   end

test/caching_test.rb

@@ -1,13 +1,16 @@
 require File.expand_path('../support/test_helper', __FILE__)
+require 'tempfile'
 
 class CachingTestTest < Minitest::Test
   def setup
     @schema = Tempfile.new(['schema', '.json'])
   end
 
   def teardown
-    @schema.close
-    @schema.unlink
+    if @schema
+      @schema.close
+      @schema.unlink
+    end
 
     JSON::Validator.clear_cache
   end