Track method calls (all of them) for the duration of a block.

call_spy.rb

def call_spy
  calls = []
  depth = 0

  set_trace_func proc { |event, file, line, id, binding, classname|
    if id != :set_trace_func
      if (event == "c-call" || event == "call")
        indent = " " * (depth * 2)
        calls << "#{indent}#{classname}##{id}"
        depth += 1

      elsif (event == "c-return" || event == "return")
        depth -= 1
      end
    end
  }

  yield
  calls

ensure
  set_trace_func(nil)
end

example.rb

require "./call_spy"
require "pathname"

calls = call_spy do
  Pathname.new(__FILE__).dirname.entries
end

$stderr.puts calls

# Output:
#
# Class#new
#   Pathname#initialize
#     Kernel#initialize_dup
#       String#initialize_copy
# Pathname#dirname
#   File#dirname
#   Pathname#initialize
#     Kernel#initialize_dup
#       String#initialize_copy
# Pathname#entries
#   Dir#entries
#     Dir#open
#     Enumerable#to_a
#       Dir#each
#   Pathname#initialize
#     Kernel#initialize_dup
#       String#initialize_copy
#   Pathname#initialize
#     Kernel#initialize_dup
#       String#initialize_copy
#   Pathname#initialize
#     Kernel#initialize_dup
#       String#initialize_copy