TDD Lesson 4

August 2, 2018

Exercise 49 of Learn Ruby the Hard Way you’re required to write the tests based on the code given to you. After working through the last exercise, this somehow made a lot more sense.

I used the Ruby docs Module on Test::Unit::Assertions for this exercise. I stuck to the assert_equal and assert_not_equal methods to test whether the ‘expected was equal to actual’ or ‘not equal to actual’ respectively and the assert_raise method to raise an exception.

The assert_raise method was tricky to work with initially as there weren’t many beginner level friendly code examples but with a bit of trial and error we got there.

The code provided in the book also required a bit of tweaking so the test file would run. Here are some examples of my test code for the exercise 49.

parsing a subject parser.rb

def self.parse_subject(word_list)
  self.skip(word_list, 'stop')
  next_word = peek(word_list)

      if next_word == 'noun'
        return self.match(word_list, 'noun')
      elsif next_word == 'verb'
        return ['noun', 'player']
      else
        raise ParserError.new("Expected a verb next.")
      end
  end

test_parser.rb

def test_parse_subject()
	assert_equal((Sentence.parse_subject([["noun", "princess"], ["verb", "eat"]])), ["noun", "princess"], ["noun", "player"])
	assert_equal((Sentence.parse_subject([["verb", "eat"],["noun", "princess"]])), ["noun", "player"])
	assert_equal((Sentence.parse_subject([["noun", "princess"], ["stop", "the"]])), ["noun", "princess"])
	assert_not_equal((Sentence.parse_subject([["verb", "eat"], ["noun", "princess"]])), ["verb", "eat"], ["verb", "player"])
	assert_raise ParserError do 
		Sentence.parse_subject(nil)
	end
	assert_raise ParserError do 
		Sentence.parse_subject(["direction", "north"])
	end
end

parsing a sentence parser.rb

def self.parse_sentence(word_list)
    subject = self.parse_subject(word_list)
    verb = self.parse_verb(word_list)
    object = self.parse_object(word_list)
  

    return Sentence.new(subject, verb, object)
  end

test_parser.rb

def test_sentence()
	sentence = Sentence.parse_sentence([["noun", "princess"], ["verb", "run"], ["stop", "the"], ["direction", "north"]])
	assert_equal(sentence.subject, "princess")
	assert_equal(sentence.object, "north")
	assert_equal(sentence.verb, "run")
end