Add tests for TestTask#verbose and TestTask#warning

The warning tests were absent at all.
The tests for verbose did not include a test for resulting
`ruby_opts_string`.

4 new asserts added

test/test_rake_test_task.rb

@@ -10,6 +10,7 @@ def test_initialize
     assert_equal :test, tt.name
     assert_equal ['lib'], tt.libs
     assert_equal 'test/test*.rb', tt.pattern
+    assert_equal false, tt.warning
     assert_equal false, tt.verbose
     assert Task.task_defined?(:test)
   end
@@ -19,14 +20,18 @@ def test_initialize_override
       t.description = "Run example tests"
       t.libs = ['src', 'ext']
       t.pattern = 'test/tc_*.rb'
+      t.warning = true
       t.verbose = true
     end
     refute_nil tt
     assert_equal "Run example tests", tt.description
     assert_equal :example, tt.name
     assert_equal ['src', 'ext'], tt.libs
     assert_equal 'test/tc_*.rb', tt.pattern
+    assert_equal true, tt.warning
     assert_equal true, tt.verbose
+    assert_match(/-w/, tt.ruby_opts_string)
+    assert_match(/--verbose/, tt.ruby_opts_string)
     assert Task.task_defined?(:example)
   end
 
@@ -142,5 +147,4 @@ def test_test_files_equals
 
     assert_equal ["a.rb", 'b.rb'], tt.file_list.to_a
   end
-
 end