NOTE: Because of formatting, I couldn’t have a curly bracket with a colon and an “o” or it turns up with some unavailable WordPress Emoticon URI. So thus I have changed items with this naming to :z_one and :z_two respectively.

Yup, still moving through all the Ruby Koans. There are, after all 276 of these things! 😉 So no more yapping, onto the notes and green lighting the tests. Cheers!

[sourcecode language=”ruby”]
def test_creating_hashes
empty_hash = Hash.new
assert_equal Hash, empty_hash.class
assert_equal({ }, empty_hash)
assert_equal 0, empty_hash.size
end

def test_hash_literals
hash = { :z_one => "uno", :z_two => "dos" }
assert_equal 2, hash.size
end

def test_accessing_hashes
hash = { :z_one => "uno", :z_two => "dos" }
assert_equal "uno", hash[:z_one]
assert_equal "dos", hash[:z_two]
assert_equal nil, hash[:doesnt_exist]
end
[/sourcecode]

From test_creating_hashes a Hash.new or {} both appear to create a new empty hash object. The second test creates and adds values to the hash. The third test has asserts that verify the data is inserted in the positions that are expected.

[sourcecode language=”ruby”]
def test_changing_hashes
hash = { :z_one => "uno", :z_two => "dos" }
hash[:z_one] = "eins"

expected = { :z_one => "eins", :z_two => "dos" }
assert_equal true, expected == hash

# Bonus Question: Why was "expected" broken out into a variable
# rather than used as a literal?
end
[/sourcecode]

Again, the hash is setup into the hash variable. Then the expected is setup in another variable. Since Ruby is pointer oriented, the expected variable is setup identical to the hash variable to assure that they truly are identical.

[sourcecode language=”ruby”]
def test_hash_is_unordered
hash1 = { :z_one => "uno", :z_two => "dos" }
hash2 = { :z_two => "dos", :z_one => "uno" }

assert_equal true, hash1 == hash2
end

def test_hash_keys
hash = { :z_one => "uno", :z_two => "dos" }
assert_equal 2, hash.keys.size
assert_equal true, hash.keys.include?(:z_one)
assert_equal true, hash.keys.include?(:z_two)
assert_equal Array, hash.keys.class
end

def test_hash_values
hash = { :z_one => "uno", :z_two => "dos" }
assert_equal 2, hash.values.size
assert_equal true, hash.values.include?("uno")
assert_equal true, hash.values.include?("dos")
assert_equal Array, hash.values.class
end
[/sourcecode]

test_hash_is_unordered shows that a hash, no matter the order the values are assigned, assigns them to the values that are directly set to.

[sourcecode language=”ruby”]
def test_combining_hashes
hash = { "jim" => 53, "amy" => 20, "dan" => 23 }
new_hash = hash.merge({ "jim" => 54, "jenny" => 26 })

assert_equal true, hash != new_hash

expected = { "jim" => __, "amy" => 20, "dan" => 23, "jenny" => __ }
assert_equal false, expected == new_hash
end
[/sourcecode]

This test asserts that the two different hashes are different, nothing amazing or odd there. The second part asserts that the next and expected hashes are different. Which again, is what we expect.

[sourcecode language=”ruby”]
def test_default_value
hash1 = Hash.new
hash1[:z_one] = 1

assert_equal 1, hash1[:z_one]
assert_equal nil, hash1[:z_two]

hash2 = Hash.new("dos")
hash2[:z_one] = 1

assert_equal 1, hash2[:z_one]
assert_equal "dos", hash2[:z_two]
end
[/sourcecode]

This test confirms that a hash with a request against a hash position that isn’t assigned to yet returns nil. The later two asserts show that a number compared to the hash position that contains a number compares as a number, and a string compared to a position that has a string also compares as equal.

Until next time, hack some koans.