fastness ➞ ack "backtrace\." lib                                                                                             ~/code/rspec
lib/spec/mocks/message_expectation.rb
159:        #error.backtrace.insert(0, @expected_from)

lib/spec/runner/backtrace_tweaker.rb
11:        return if error.backtrace.nil?
12:        error.backtrace.each do |line|
42:        return if error.backtrace.nil?
43:        error.backtrace.collect! do |line|
53:        error.backtrace.compact!

lib/spec/runner/formatter/base_text_formatter.rb
90:          return "" if backtrace.nil?
91:          backtrace.map { |line| backtrace_line(line) }.join("\n")

lib/spec/runner/formatter/story/plain_text_formatter.rb
74:    #{err.backtrace.join("\n")}

lib/spec/runner/spec_parser.rb
36:        parsed_backtrace.each do |example_file, example_line|
47:        parsed_backtrace.each do |example_file, example_line|
64:        backtrace.collect do |trace_line|