Random letter prefix to CUID2

This commit introduces a random letter prefix to the CUID2 generation
process. This change is intended to reduce the likelihood of CUID2
collisions. The random letter is generated from the range 'a' to 'z'.

The tests have been updated to reflect this change. A new test has been
added to ensure that CUID2s do not have the same first character. The
collision test run and CUID2s per run values have been reduced for
testing purposes.

The version of the library has been bumped to 1.0.1.

lib/cuid2.rb

@@ -42,6 +42,7 @@ def self.create(input, length = BIG_LENGTH)
 
  class << self
  def call(length = DEFAULT_LENGTH)
+ random_letter = ('a'..'z').to_a[(rand * 26).floor]
  hash_input = (time + Entropy.create(length) + count + fingerprint).to_s
 
  "#{random_letter}#{Cuid2::Hash.create(hash_input, length)[2..length]}"
@@ -67,10 +68,6 @@ def counter
  (rand + 1) * 2057
  end
 
- def random_letter
- ('a'..'z').to_a[(random * 26).floor]
- end
-
  def fingerprint
  Cuid2::Hash.create("#{((random + 1) * 2063).floor} #{Object.constants.map(&:to_s)}")
  end

lib/cuid2/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Cuid2
- VERSION = '1.0.0'
+ VERSION = '1.0.1'
 end

spec/cuid2_spec.rb

@@ -2,8 +2,8 @@
 
 require 'cuid2'
 
-COLISION_TEST_RUN = ENV.fetch('COLISION_TEST_RUN', 10).to_i
-CUIDS_PER_RUN = ENV.fetch('CUIDS_PER_RUN', 100).to_i
+COLISION_TEST_RUN = ENV.fetch('COLISION_TEST_RUN', 1).to_i
+CUIDS_PER_RUN = ENV.fetch('CUIDS_PER_RUN', 10).to_i
 
 RSpec.describe Cuid2 do
  it 'has a version number' do
@@ -25,4 +25,27 @@
  expect(cuids.uniq.sort).to eq(cuids.sort)
  expect(cuids.sample).to match(/[a-z0-9]{24}/)
  end
+
+ it 'should not collide with prefix' do
+ cuids = []
+ COLISION_TEST_RUN.times do
+ CUIDS_PER_RUN.times do
+ cuids << Cuid2.call(prefix: 'test')
+ end
+ end
+ expect(cuids.uniq.size).to eq(cuids.size)
+ expect(cuids.size).to eq(COLISION_TEST_RUN * CUIDS_PER_RUN)
+ expect(cuids.uniq.size).to eq(COLISION_TEST_RUN * CUIDS_PER_RUN)
+ expect(cuids.uniq.sort).to eq(cuids.sort)
+ expect(cuids.sample).to match(/test[a-z0-9]{24}/)
+ end
+
+ it 'should not have the same first character' do
+ cuids = []
+ 5000.times do
+ cuids << Cuid2.call[0]
+ end
+
+ expect(cuids.uniq.size).to be > 1
+ end
 end