Adding assert function - ruby-on-rails

Question

I'm new to Ruby on Rails and going through Learn Ruby the Hard Way right now. In the lesson I am supposed to add the Assert feature to Dict.rb (shown below). Would anyone know how I can go about doing this? Every time I try I receive an error.
module Dict
#Creates a new function that makes a Dictionary. This is done through creating the
# aDict variable that has an array in which num_buckets array is placed inside.
# These buckets will be used to hold the contents of the Dict and later aDict.length
# is used to find out how many buckets there are.
def Dict.new(num_buckets=256)
# Initializes a Dict with the given number of buckets.
aDict = []
(0...num_buckets).each do |i|
aDict.push([])
end
return aDict
end
# Converts a string to a number using the bult-in Ruby 'hash' function
# Once I have a number for the key, I use the % operator and aDict.length to get a
# bucket where the remainder can go.
def Dict.hash_key(aDict, key)
# Given a key this will create a number and then convert it to an index for the
# aDict's buckets
return key.hash % aDict.length
end
# Uses hash_key to find a bucket that the key could be in. Using bucket_id I can get
# the bucket where the key could be. By using the modulus operator I know it will fit
# into the aDict array of 256.
def Dict.get_bucket(aDict, key)
# Given a key, find the bucket where it would go.
bucket_id = Dict.hash_key(aDict, key)
return aDict[bucket_id]
end
# Uses get_slot to get the (i, k, v) and returns the v (value) only.
def Dict.get_slot(aDict, key, default=nil)
# Returns the index, key and value of a slot found in a bucket.
bucket = Dict.get_bucket(aDict, key)
bucket.each_with_index do |kv, i|
k, v = kv
if key == k
return i, k, v
end
end
return -1, key, default
end
def Dict.get(aDict, key, default=nil)
# Gets the value in a bucket for the given key or the default.
i, k, v = Dict.get_slot(aDict, key, default=default)
return v
end
# Sets a key/value pair by getting the bucket and appending the new (key, value) to it.
# First you have to get the bucket, see if the key already exists, if it does then
# replace it, if it doesn't get replaced then append it.
def Dict.set(aDict, key, value)
# Sets the key to the value, replacing any existing value.
bucket = Dict.get_bucket(aDict, key)
i, k, v = Dict.get_slot(aDict, key)
if i >= 0
bucket[i] = [key, value]
else
bucket.push([key, value])
end
end
# Deletes a key by getting the bucket, searching for key in it and deleting it form the
# array.
def Dict.delete(aDict, key)
# Deletes the given key from the Dict.
bucket = Dict.get_bucket(aDict, key)
(0...bucket.length).each do |i|
k, v = bucket[i]
if key == k
bucket.delete_at(i)
break
end
end
end
# goes through each slot in each bucket and prints out what's in the Dict.
def Dict.list(aDict)
# Prints out what's in the Dict.
aDict.each do |bucket|
if bucket
bucket.each {|k, v| puts k, v}
end
end
end
end
I am using the following script to run methods from the module Dict.rb:
require './dict.rb'
# create a mapping of state to abbreviation
states = Dict.new()
Dict.set(states, 'Oregon', 'OR')
Dict.set(states, 'Florida', 'FL')
Dict.set(states, 'California', 'CA')
Dict.set(states, 'New York', 'NY')
Dict.set(states, 'Michigan', 'MI')
# create a basic set of states and some cities in them
cities = Dict.new()
Dict.set(cities, 'CA', 'San Francisco')
Dict.set(cities, 'MI', 'Detroit')
Dict.set(cities, 'FL', 'Jacksonville')
# add some more cities
Dict.set(cities, 'NY', 'New York')
Dict.set(cities, 'OR', 'Portland')
# puts out some cities
puts '-' * 10
puts "NY State has: #{Dict.get(cities, 'NY')}"
puts "OR State has: #{Dict.get(cities, 'OR')}"
# puts some states
puts '-' * 10
puts "Michigan's abbreviation is: #{Dict.get(states, 'Michigan')}"
puts "Florida's abbreviation is: #{Dict.get(states, 'Florida')}"
# do it by using the state then cities dict
puts '-' * 10
puts "Michigan has: #{Dict.get(cities, Dict.get(states, 'Michigan'))}"
puts "Florida has: #{Dict.get(cities, Dict.get(states, 'Florida'))}"
# puts every state abbreviation
puts '-' * 10
Dict.list(states)
# puts every city in state
puts '-' * 10
Dict.list(cities)
puts '-' * 10
# by default ruby says "nil" when something isn't in there
state = Dict.get(states, 'Texas')
if !state
puts "Sorry, no Texas."
end
# default values using ||= with the nil result
city = Dict.get(cities, 'TX', 'Does Not Exist')
puts "The city for the state 'TX' is: #{city}"

Answer 1

There is no "assert" method by default in Ruby. That's why you are getting an "undefined method" error. You either need to implement this method yourself or use a testing framework like Minitest or Rspec.
If you want to implement a simple assert method yourself it would be something like this:
def assert(first_item, second_item)
unless first_item == second_item
puts "[Error] #{first_item} does not equal #{second_item}"
end
end
And then use it like this:
assert(Dict.get(cities, 'NY'), 'New York')
The idea is that assertions help you make sure your code returns the expected output without having to check it manually.