diff --git a/judge/scripts/test/engine_test.rb b/judge/scripts/test/engine_test.rb
new file mode 100644
--- /dev/null
+++ b/judge/scripts/test/engine_test.rb
@@ -0,0 +1,152 @@
+require 'test/unit'
+require 'rubygems'
+require 'mocha'
+
+require File.join(File.dirname(__FILE__),'test_helper')
+
+class GraderEngineTest < UnitTest.TestCase
+
+  def setup
+    @@lang_c = stub(:name => 'c', :ext => 'c')
+    @@lang_cpp = stub(:name => 'cpp', :ext => 'cpp')
+    @@lang_pas = stub(:name => 'pas', :ext => 'pas')
+
+    @config = Grader::Configuration.get_instance
+
+    @problem_test1 = stub(:id => 1, :name => 'test1', :full_score => 135)
+    @user_user1 = stub(:id => 1, :login => 'user1')
+
+    @engine = Grader::Engine.new    
+
+    init_sandbox
+  end
+
+  def teardown
+  end
+
+  def test_grade_oldest_task_with_no_submission
+    Task.expects(:get_inqueue_and_change_status).returns(nil)
+    assert_equal nil, @engine.grade_oldest_task, 'should return nil when there is no task'
+  end
+
+  def test_normal_submission
+    submission = create_test1_submission_mock_from_file("test1_correct.c")
+
+    submission.expects(:graded_at=)
+    submission.expects(:points=).with(135)
+    submission.expects(:grader_comment=).with do |value|
+      /^PASSED/.match(value)
+    end
+    submission.expects(:compiler_message=).with('')
+    submission.expects(:save)
+
+    @engine.grade(submission)
+  end
+
+  def test_compile_error_submission
+    submission = create_test1_submission_mock_from_file("test1_compile_error.c")
+
+    submission.expects(:graded_at=)
+    submission.expects(:points=).with(0)
+    submission.expects(:grader_comment=).with('FAILED: compile error')
+    submission.expects(:compiler_message=) do |value|
+      /[Ee]rror/.match value
+    end
+    submission.expects(:save)
+
+    @engine.grade(submission)
+  end
+
+  def test_timeout_submission
+    @problem_test2 = stub(:id => 1, :name => 'test2', :full_score => 10)
+    @user_user1 = stub(:id => 1, :login => 'user1')
+
+    submission = create_submission_from_file(1, @user_user1, @problem_test2,
+                                             "test2_timeout.c")
+
+    submission.expects(:graded_at=)
+    submission.expects(:points=).with(0)
+    submission.expects(:grader_comment=).with do |value|
+      /^FAILED: TT$/.match value
+    end
+    submission.expects(:compiler_message=).with('')
+    submission.expects(:save)
+
+    @engine.grade(submission)
+  end
+
+  def test_timeout_submission_running_one_and_a_half_second
+    @problem_test2 = stub(:id => 1, :name => 'test2', :full_score => 20)
+    @user_user1 = stub(:id => 1, :login => 'user1')
+
+    submission = create_submission_from_file(1, @user_user1, @problem_test2,
+                                             "test2_1-5sec.c")
+
+    submission.expects(:graded_at=)
+    submission.expects(:points=).with(10)
+    submission.expects(:grader_comment=).with do |value|
+      /^FAILED: TP$/.match value
+    end
+    submission.expects(:compiler_message=).with('')
+    submission.expects(:save)
+
+    @engine.grade(submission)
+  end
+
+  def test_grade_oldest_task
+    # mock submission
+    submission = create_test1_submission_mock_from_file("test1_correct.c")
+
+    submission.expects(:graded_at=)
+    submission.expects(:points=).with(135)
+    submission.expects(:grader_comment=).with do |value|
+      /^PASSED/.match(value)
+    end
+    submission.expects(:compiler_message=).with('')
+    submission.expects(:save)
+
+    # mock task
+    task = stub(:id => 1, :submission_id => submission.id)
+    Task.expects(:get_inqueue_and_change_status).returns(task)
+    task.expects(:status_complete!)
+
+    # mock Submission
+    Submission.expects(:find).with(task.submission_id).returns(submission)
+
+    @engine.grade_oldest_task
+  end
+
+  def test_grade_oldest_task_with_grader_process
+    grader_process = stub
+    grader_process.expects(:report_active)
+
+    @engine = Grader::Engine.new(grader_process)
+
+    test_grade_oldest_task
+  end
+
+  protected
+
+  def clear_sandbox
+    clear_cmd = "rm -rf #{@config.test_sandbox_dir}/*"
+    system(clear_cmd)
+  end
+
+  def init_sandbox
+    clear_sandbox
+    Dir.mkdir @config.user_result_dir
+    cp_cmd = "cp -R #{@config.test_data_dir}/ev #{@config.test_sandbox_dir}"
+    system(cp_cmd)
+  end
+
+  def create_submission_from_file(id, user, problem, source_fname, language = @@lang_c)
+    source = File.open(@config.test_data_dir + "/" + source_fname).read
+    stub(:id => id, :user => user, :problem => problem,
+         :source => source, :language => language)
+  end
+
+  def create_test1_submission_mock_from_file(source_fname)
+    create_submission_from_file(1, @user_user1, @problem_test1, source_fname)
+  end
+  
+end