Rails: test code in lib directory with RubyTest with Sublime Text 2

I would like test code in the lib directory of Rails. I use RubyTest to work in Sublime Text 2. My library is in lib/my_lib.

module MyLib
    def self.get_zero
        0
    end
end

My unit test is in test/unit/lib/my_lib

require 'test/unit'
require 'my_lib/my_class_to_test'

module MyLib
    class MyClassToTestTest < Test::Unit::TestCase
        def test_zero
            assert_equal(0, MyLib::get_zero)
        end
end
end

Unit tests pass when I run them with the command line:

rake test:units

To save time I can run only my unit test with this command line:

ruby -I"lib" test/unit/lib/my_lib/my_class_to_test_test.rb

I would like use RubyTest with Sublime Text 2 but when I use it (Maj+Ctrl+R) I obtain error :

test/unit/lib/my_lib/my_class_to_test_test.rb:3:in `require': no such file to load -- my_lib/my_class_to_test (LoadError)
    from test/unit/lib/my_lib/my_class_to_test_test.rb:3

How RubyTest could load the lib directory in the path ?

The configuration file of RubyTest in Sublime Text 2 is here:

~/.config/sublime-text-2/Packages/RubyTest/RubyTest.sublime-settings

I added lib to the -I option in the ruby_unit_exec like that:

"ruby_unit_exec": "ruby -Ilib:test"`

The problem is fixed.