even_better.rb

# Original method

#def process(input)
#  if input == 'q'
#    puts 'Goodbye'
#  elsif input == 'tweet'
#    puts 'tweeting'
#  elsif input == 'dm'
#    puts 'direct messaging'
#  elsif input == 'help'
#    puts 'helping'
#  end
#end

RESPONSES = {
  'tweet' => 'tweeting',
  'dm'    => 'direct messaging',
  'help'  => 'helping',
  'q'     => 'Goodbye'
}

def process(input)
  puts RESPONSES.fetch(input) { return nil }
end

even_better_spec.rb

describe 'process' do
  it 'prints "Goodbye" when called with input of "q"' do
    STDOUT.should_receive(:puts).with('Goodbye')
    process('q')
  end

  it 'prints "tweeting" when called with input of "tweet"' do
    STDOUT.should_receive(:puts).with('tweeting')
    process('tweet')
  end

  it 'prints "direct messaging" when called with input of "dm"' do
    STDOUT.should_receive(:puts).with('direct messaging')
    process('dm')
  end

  it 'prints "helping" when called with input of "help"' do
    STDOUT.should_receive(:puts).with('helping')
    process('help')
  end

  it 'returns nil when called with any other input ' do
    STDOUT.should_not_receive(:puts)
    expect(process('bad input')).to eq(nil)
  end
end