Add more tests for invalid <label> directive

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

lib/fluent/root_agent.rb

@@ -131,7 +131,7 @@ def configure(conf)
         end
         name = e.arg
         raise ConfigError, "Missing symbol argument on <label> directive" if name.empty?
-        raise ConfigError, "@ROOT for <label> is invalid, reserved for getting root router" if name == '@ROOT'
+        raise ConfigError, "@ROOT for <label> is not permitted, reserved for getting root router" if name == '@ROOT'
 
         if name == ERROR_LABEL
           error_label_config = e

test/test_root_agent.rb

@@ -109,6 +109,34 @@ def configure_ra(conf_str)
       end
     end
 
+    test 'raises configuration error for label without name' do
+      conf = <<-EOC
+<label>
+  @type test_out
+</label>
+EOC
+      errmsg = "Missing symbol argument on <label> directive"
+      assert_raise Fluent::ConfigError.new(errmsg) do
+        configure_ra(conf)
+      end
+    end
+
+    test 'raises configuration error for <label @ROOT>' do
+      conf = <<-EOC
+<source>
+  @type test_in
+  @label @ROOT
+</source>
+<label @ROOT>
+  @type test_out
+</label>
+EOC
+      errmsg = "@ROOT for <label> is not permitted, reserved for getting root router"
+      assert_raise Fluent::ConfigError.new(errmsg) do
+        configure_ra(conf)
+      end
+    end
+
     test 'raises configuration error if there are not match sections in label section' do
       conf = <<-EOC
 <source>