Demonstration of block binding differences in Ruby

block_binding.rb

class Expectation
  def to(matcher = nil, &block)
    if block_given?
      puts "block passed to `to` method"
      yield
    end
  end
end

def expect
  Expectation.new
end

def have_logged(&block)
  if block_given?
    puts "block passed to `have_logged` method"
    yield
  end
end

expect do
  # This will bind to `have_logged`
end.to have_logged {
  puts "called with { }"
}
# block passed to `have_logged` method
# called with { }

expect do
  # This will bind to `to`
end.to have_logged do
  puts "called with do/end"
end
# block passed to `to` method
# called with do/end