Add a helper to start debug session with the test program

[st0012]

When writing tests, sometimes we may test the script manually. But currently this could take a few steps:

1. Copy the test program into a file, say target.rb
2. Remove all the line numbers.
3. Run exe/rdbg -e target.rb from the terminal.

And whenever we change the script or switched to another test case, we need to go through these steps again.

So in the PR, I introduced a new helper called _start_manual_debug_session(program). You can place it in any test case:

def program
  # ....
end

def test_something_about_debugger
  _start_manual_debug_session(program) # just add this line
  debug_code(program) do
    # your original test code
  end
end

And then run the test case as you usually do, it'll enter a debug session with your test script 😄

(btw, the remote debugging session is pretty neat. I love it 😍 )

[ono-max]

I'm concerned that this method should be placed in utils.rb because I suppose that test files are script files that can be tested automatically such as rake test.

[st0012]

I don't get the concern. it's not suppose to be committed to the final test scripts, it's only used when "writing" the scripts.
or are you worry about the method visibility? I just defined it as a private method though

[ono-max]

Ok, it looks fine to me. The method visibility is also good.