Use ruby -w by default

lib/rake/testtask.rb

@@ -83,7 +83,7 @@ def initialize(name=:test)
       @options = nil
       @test_files = nil
       @verbose = false
-      @warning = false
+      @warning = true
       @loader = :rake
       @ruby_opts = []
       yield self if block_given?

test/test_rake_test_task.rb

@@ -11,20 +11,21 @@ def test_initialize
     assert_equal ['lib'], tt.libs
     assert_equal 'test/test*.rb', tt.pattern
     assert_equal false, tt.verbose
+    assert_equal true, tt.warning
     assert Task.task_defined?(:test)
   end
 
   def test_initialize_override
     tt = Rake::TestTask.new(:example) do |t|
       t.libs = ['src', 'ext']
       t.pattern = 'test/tc_*.rb'
-      t.verbose = true
+      t.verbose = false
     end
     refute_nil tt
     assert_equal :example, tt.name
     assert_equal ['src', 'ext'], tt.libs
     assert_equal 'test/tc_*.rb', tt.pattern
-    assert_equal true, tt.verbose
+    assert_equal false, tt.verbose
     assert Task.task_defined?(:example)
   end
 
@@ -46,12 +47,13 @@ def test_libs_equals
 
     path = %w[lib A B].join File::PATH_SEPARATOR
 
-    assert_equal "-I\"#{path}\"", test_task.ruby_opts_string
+    assert_equal "-w -I\"#{path}\"", test_task.ruby_opts_string
   end
 
   def test_libs_equals_empty
     test_task = Rake::TestTask.new do |t|
-      t.libs = []
+      t.libs    = []
+      t.warning = false
     end
 
     assert_equal '', test_task.ruby_opts_string