diff --git a/test/models/fluentd/agent_test.rb b/test/models/fluentd/agent_test.rb
new file mode 100644
index 0000000..6804883
--- /dev/null
+++ b/test/models/fluentd/agent_test.rb
@@ -0,0 +1,279 @@
+require "test_helper"
+
+class Fluentd
+  class AgentTest < ActiveSupport::TestCase
+    module CommonBehavior
+      extend ActiveSupport::Concern
+      included do
+        sub_test_case "#extra_options" do
+          test "blank" do
+            @agent = @klass.new({})
+            assert_equal({}, @agent.extra_options)
+            extra_options = {
+              config_file: @agent.config_file,
+              log_file: @agent.log_file,
+              pid_file: @agent.pid_file
+            }
+            assert_equal(extra_options, @klass.default_options)
+          end
+
+          test "given" do
+            options = {
+              config_file: "pid",
+              log_file: "log",
+              pid_file: "config"
+            }
+            @agent = @klass.new(options)
+            extra_options = {
+              config_file: @agent.config_file,
+              log_file: @agent.log_file,
+              pid_file: @agent.pid_file
+            }
+            assert_equal(extra_options, options)
+          end
+        end
+
+        sub_test_case "#errors_since" do
+          setup do
+            @logged_time = Time.parse('2014-05-27')
+            @now = Time.parse("2014-05-29")
+            Timecop.freeze(@now)
+          end
+
+          teardown do
+            Timecop.return
+          end
+
+          test "have no errors" do
+            stub(@agent).log_file { fixture_path("error0.log") }
+            assert do
+              @agent.log.errors_since(100.days.ago).empty?
+            end
+          end
+
+          sub_test_case "have errors" do
+            test "unreachable since 0 days ago" do
+              stub(@agent).log_file { fixture_path("error2.log") }
+              assert_equal([], @agent.log.errors_since(0.days.ago))
+            end
+
+            test "reachable since 100 days ago" do
+              stub(@agent).log_file { fixture_path("error2.log") }
+              logs = @agent.log.errors_since(100.days.ago)
+              assert do
+                logs[0][:subject].include?("Address already in use - bind(2)")
+              end
+              one = Time.parse(logs[0][:subject])
+              two = Time.parse(logs[1][:subject])
+              assert do
+                one >= two
+              end
+            end
+          end
+        end
+
+        sub_test_case "#recent_errors" do
+          test "have 0 error log" do
+            stub(@agent).log_file { fixture_path("error0.log") }
+            assert do
+              @agent.log.recent_errors(2).empty?
+            end
+          end
+
+          sub_test_case "have 2 error log" do
+            setup do
+              stub(@agent).log_file { fixture_path("error2.log") }
+            end
+
+            data("limit 1" => 1,
+                 "limit 2" => 2)
+            test "limit" do |limit|
+              assert do
+                limit == @agent.log.recent_errors(limit).size
+              end
+            end
+
+            test "contains stack trace" do
+              logs = @agent.log.recent_errors(2)
+              assert do
+                logs[0][:subject].include?("Address already in use - bind(2)")
+              end
+            end
+
+            test "newer(bottom) is first" do
+              logs = @agent.log.recent_errors(2)
+              one = Time.parse(logs[0][:subject])
+              two = Time.parse(logs[1][:subject])
+              assert do
+                one >= two
+              end
+            end
+          end
+
+          sub_test_case "have 3 errors log including sequential 2 error log" do
+            setup do
+              stub(@agent).log_file { fixture_path("error3.log") }
+            end
+
+            test "count 3 errors" do
+              logs = @agent.log.recent_errors(3)
+              assert_equal(logs[0][:subject].slice(/::EADDRINUSE: (\d) Address already in use/, 1), "3")
+              assert_equal(logs[0][:notes].size, 1)
+              assert_equal(logs[1][:subject].slice(/::EADDRINUSE: (\d) Address already in use/, 1), "2")
+              assert_equal(logs[1][:notes].size, 2)
+              assert_equal(logs[2][:subject].slice(/::EADDRINUSE: (\d) Address already in use/, 1), "1")
+              assert_equal(logs[2][:notes].size, 0)
+            end
+          end
+        end
+
+        sub_test_case "#dryrun" do
+          setup do
+            pend("/usr/sbin/td-agent does not exist") unless File.exist?("/usr/sbin/td-agent")
+            @root = FluentdUI.data_dir + "/tmp/agent-test/"
+            @dummy_log_file = @root + "dummy.log"
+            @dummy_pid_file = @root + "dummy.pid"
+
+            FileUtils.mkdir_p(@root)
+            stub(@agent).log_file { @dummy_log_file }
+            stub(@agent).pid_file { @dummy_pid_file }
+          end
+
+          sub_test_case "valid/invalid" do
+            setup do
+              @config_path = Rails.root.join("tmp", "fluent-test.conf").to_s
+            end
+
+            teardown do
+              File.unlink(@config_path) if @config_path && File.exist?(@config_path)
+            end
+
+            test "valid config" do
+              config = <<-CONF.strip_heredoc
+              <source>
+                @type forward
+              </source>
+              CONF
+              File.write(@config_path, config)
+              assert_nothing_raised do
+                @agent.dryrun!(@config_path)
+              end
+              assert_true(@agent.dryrun(@config_path))
+            end
+
+            test "invalid config" do
+              config = <<-CONF.strip_heredoc
+              <source>
+                @type forward
+              CONF
+              File.write(@config_path, config)
+              assert_raise(Fluentd::Agent::ConfigError) do
+                @agent.dryrun!(@config_path)
+              end
+              assert_false(@agent.dryrun(@config_path))
+            end
+          end
+        end
+      end
+    end
+
+    sub_test_case "FluentdGem" do
+      setup do
+        options = {
+          config_file: Rails.root.join("tmp", "fluentd-test", "fluentd.conf").to_s
+        }
+        @klass = Fluentd::Agent::FluentdGem
+        @agent = @klass.new(options)
+      end
+
+      include CommonBehavior
+
+      test "#options_to_argv" do
+        expected_argv = " -c #{@agent.config_file} -d #{@agent.pid_file} -o #{@agent.log_file}"
+        assert_equal(expected_argv, @agent.__send__(:options_to_argv))
+      end
+
+      sub_test_case "#start" do
+        setup do
+          # ensure valid config
+          @agent.config_write("")
+        end
+
+        teardown do
+          FileUtils.rm_rf(@agent.running_config_backup_dir)
+        end
+
+        test "running" do
+          stub(@agent).running? { true }
+          assert_true(@agent.start)
+        end
+
+        test "succeeded to actual_start" do
+          stub(@agent).running? { false }
+          stub(@agent).actual_start { true }
+          assert_true(@agent.start)
+          backup_file = @agent.running_config_backup_file
+          assert do
+            File.exist?(backup_file)
+          end
+          assert_equal(File.read(@agent.config_file), File.read(backup_file))
+        end
+
+        test "failed to actual_start" do
+          stub(@agent).running? { false }
+          stub(@agent).actual_start { false }
+          assert_nil(@agent.start)
+        end
+      end
+
+      sub_test_case "#stop" do
+        data("succeeded to actual_stop" => true,
+             "failed to actual_stop" => false)
+        test "running" do |stop_result|
+          stub(@agent).running? { true }
+          stub(@agent).actual_stop { stop_result }
+          assert_equal(stop_result, @agent.stop)
+        end
+
+        test "not running" do
+          stub(@agent).running? { false }
+          assert do
+            @agent.stop
+          end
+        end
+      end
+    end
+
+    sub_test_case "TdAgent" do
+      setup do
+        options = {
+          config_file: Rails.root.join("tmp", "fluentd-test", "fluentd.conf").to_s
+        }
+        @klass = Fluentd::Agent::TdAgent
+        @agent = @klass.new(options)
+      end
+
+      include CommonBehavior
+
+      sub_test_case "#backup_running_config" do
+        setup do
+          stub(@agent).detached_command { true }
+          stub(@agent).pid_from_launchctl { true }
+          @agent.config_write("") # ensure valid config
+        end
+
+        teardown do
+          FileUtils.rm_rf(@agent.running_config_backup_dir)
+        end
+
+
+        test "backup running conf" do
+          @agent.start
+          backup_file = @agent.running_config_backup_file
+          assert_true(File.exist?(backup_file))
+          assert_equal(File.read(@agent.config_file), File.read(backup_file))
+        end
+      end
+    end
+  end
+end