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Narf: A Ruby Micro Test Framework

11 February 2011

I’m a happy user of RSpec, Cucumber and sometimes Steak. Great tools to write specs and features and prove my application does what it’s supposed to do. But sometimes I have the need for something more light weight. ~ For example, sometimes I need to write a single ruby method. Just something ‘quick’ to import a file, convert some data or whatever. Being a good citizen I want to test that method.

Using RSpec or Cucumber here just seems wrong here. So, I’ve implemented my own Ruby Micro Test Framework: Narf

def assert(message, &block)
  puts "#{"%6s" % ((yield || false) ? '  PASS' : '! FAIL')} - #{message}"
end

(Yes, that’s it.)

With this simple method, added to your ruby file, you can test your method. And example:

Let’s say you’re going to write a method that counts how often the word ‘ruby’ occurs in a given String:

def count_rubies(text)
  # TODO
end

#--- Ruby Micro Test Framework
def assert(message, &block)
  puts "#{"%6s" % ((yield || false) ? '  PASS' : '! FAIL')} - #{message}"
end
#---

#--- Tests
assert "Count zero rubies" do
  count_rubies("this is Sparta!") == 0
end

assert "Count one ruby" do
  count_rubies("This is one ruby") == 1
end

assert "Count one RuBy" do
  count_rubies("This is one RuBy") == 1
end

Now, simple save this file and feed it to ruby:

$ ruby my_method.rb
! FAIL - Count zero rubies
! FAIL - Count one ruby
! FAIL - Count one RuBy

Now, implement your method…

def count_rubies(text)
  text.match(/(ruby)/i).size
end

And re-run your tests:

$ ruby my_method.rb
  PASS - Count zero rubies
  PASS - Count one ruby
  PASS - Count one RuBy

So with the addition of just a single method you can fully TDD/BDD your single method Ruby code. Pretty need, huh?

Need codez?