```ruby
require 'pp'

class Knowledge

  def ask string
    q = Question.new "?"
    ! q.well_formed?
  end

end

class Question

  def initialize string
  end

  def well_formed?
  end

end

diag = []

tracer = Proc.new do |event, file, line, method, binding, class_name|
  if %w[ call return ].include? event
  puts <<-OUT
event:      #{ event }
line:       #{ line }
method:     #{ method }
class_name: #{ class_name }
self:       #{ binding.eval('self') }

OUT

  diag << {:message => method}
  end
end

set_trace_func tracer

Knowledge.new.ask 1

set_trace_func nil

def assert(value, expected = true)
  if value == expected
    puts '.'
  else
    raise "#{value} != #{expected}"
  end
end

assert diag[0][:message], :ask
```

Test sender and receiver of first node
user
```ruby
require 'pp'

class Knowledge

  def ask string
    q = Question.new "?"
    ! q.well_formed?
  end

end

class Question

  def initialize string
  end

  def well_formed?
  end

end

diag = []

tracer = Proc.new do |event, file, line, method, binding, class_name|
  if %w[ call return ].include? event
  puts <<-OUT
event:      #{ event }
line:       #{ line }
method:     #{ method }
class_name: #{ class_name }
self:       #{ binding.eval('self') }

OUT

  diag << {:message => method, :receiver => binding.eval('self')}
  end
end

set_trace_func tracer

Knowledge.new.ask 1

set_trace_func nil

def assert(value, expected = true)
  if expected == value || ( expected.respond_to?(:match) && expected.match(value) )
    puts '.'
  else
    raise "#{ value.inspect } != #{ expected.inspect }"
  end
end

assert diag[0][:message], :ask
assert diag[0][:sender], nil
assert diag[0][:receiver].inspect, /#\<Knowledge:.+>/
```
assistant