TDD Lesson 2

July 13, 2018

This month’s blogging has been a little slow because it is taking a while for me to get my head around TDD. I have no complaints though because this has been another steep learning curve requiring a significant amount of external research.

Continuing on from the last post, I have been working through writing the code for a given test with two assertions. In this post I’m working through the second assertion - which took a while.

To recap the test was: test_lexicon.rb

require 'ex48/lexicon.rb'
require "test/unit"

class TestLexicon < Test::Unit::TestCase

  def test_directions()
    assert_equal(Lexicon.scan("north"), [['direction', 'north']])
    result = Lexicon.scan("north south east")

    assert_equal(result, [['direction', 'north'],
           ['direction', 'south'],
           ['direction', 'east']])
  end
end

The corresponding code that I wrote was: lexicon.rb

class Lexicon

	 	@@hash = {
	 		'direction' => ['south', 'north', 'east']
		}

	def self.scan(sentence)
		words = sentence.split(' ')
		result = [] # this array should contain arrays of [key word]

		words.each do |word|
			element = [] # push this array of [key,word] to the result array
				@@hash.each do |key, value|
					if value.include?(word)
					element = [key, word]
					result.push(element) 
					end
				end
		end
				return result
	end
		
end

The error I kept receiving was:

Started
F
===========================================================================================================================
/Users/wickinot/Code/learnrubythehardway/ex48/tests/test_lexicon.rb:11:in `test_directions'
      8:     assert_equal(Lexicon.scan("north"), [['direction', 'north']])
      9:     result = Lexicon.scan("north south east")
     10: 
  => 11:     assert_equal(result, [['direction', 'north'], 
     12:     	['direction', 'south'],['direction', 'east']])
     13:   end
     14: end
<[["direction", "north"]]> expected but was
<[["direction", "north"], ["direction", "south"], ["direction", "east"]]>

diff:
? [["direction", "north"], ["direction", "south"], ["direction", "east"]]
Failure: test_directions(TestLexicon)
===========================================================================================================================

Finished in 0.008249 seconds.
---------------------------------------------------------------------------------------------------------------------------
1 tests, 1 assertions, 1 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
0% passed
---------------------------------------------------------------------------------------------------------------------------
121.23 tests/s, 121.23 assertions/s
rake aborted!

The reason for the error was that the code was not pushing the element array to the result array. This is because I missed that I never specified the element array. To figure out the solution I did do a lot of research on the internet and also came across another excellent resource - a book called Eloquent Ruby by Russ Olsen. Though these resources did not give me the answer to the solution, they did make me research and understand hashes and arrays and iteration on a deeper level. For example, the hash code is a lot less repetitive.