test: add interface tests for metrics

Signed-off-by: Shizuo Fujita <fujita@clear-code.com>

Author: Watson1978

test/plugin/test_out_forward.rb

@@ -1395,4 +1395,15 @@ def plugin_id_for_test?
       end
     end
   end
+
+  test 'can use metrics plugins and fallback methods' do
+    @d = create_driver
+
+    %w[healthy_nodes_count_metrics registered_nodes_count_metrics].each do |metric_name|
+      assert_true @d.instance.instance_variable_get(:"@#{metric_name}").is_a?(Fluent::Plugin::Metrics)
+    end
+
+    assert_equal 0, @d.instance.healthy_nodes_count
+    assert_equal 0, @d.instance.registered_nodes_count
+  end
 end

test/plugin/test_output.rb

@@ -226,17 +226,21 @@ def waiting(seconds)
     test 'can use metrics plugins and fallback methods' do
       @i.configure(config_element())
 
-      %w[num_errors_metrics emit_count_metrics emit_size_metrics emit_records_metrics
-         write_count_metrics rollback_count_metrics flush_time_count_metrics slow_flush_count_metrics].each do |metric_name|
+      %w[num_errors_metrics emit_count_metrics emit_size_metrics emit_records_metrics write_count_metrics
+         write_secondary_count_metrics rollback_count_metrics flush_time_count_metrics slow_flush_count_metrics].each do |metric_name|
         assert_true @i.instance_variable_get(:"@#{metric_name}").is_a?(Fluent::Plugin::Metrics)
       end
 
       assert_equal 0, @i.num_errors
       assert_equal 0, @i.emit_count
+      assert_equal 0, @i.emit_records
       assert_equal 0, @i.emit_size
       assert_equal 0, @i.emit_records
       assert_equal 0, @i.write_count
+      assert_equal 0, @i.write_secondary_count
       assert_equal 0, @i.rollback_count
+      assert_equal 0, @i.flush_time_count
+      assert_equal 0, @i.slow_flush_count
     end
 
     data(:new_api => :chunk,