Merge pull request #64 from k2nr/bquorning/improve-ulid-validator

Test and improve #valid_ulid? method

lib/ulid/rails/type.rb

@@ -44,15 +44,21 @@ def cast_string_to_ulid(value, data_class: Data)
       end
 
       class Data < ActiveModel::Type::Binary::Data
+        INVALID_CHARACTERS_REGEX = /[ilou]/i.freeze
+        VALID_INITIAL_CHARACTER_REGEX = /^[0-7]/i.freeze
+
         def self.from_serialized(data)
           deserialized = Base32::Crockford.encode(data.hex).rjust(26, "0")
           new(deserialized)
         end
 
         def self.valid_ulid?(str)
           return true if str.nil?
+          return false unless str.length == 26
+          return false if INVALID_CHARACTERS_REGEX.match?(str)
+          return false unless VALID_INITIAL_CHARACTER_REGEX.match?(str)
 
-          str.length == 26 && Base32::Crockford.valid?(str)
+          Base32::Crockford.valid?(str)
         end
 
         def initialize(value)

test/ulid/rails/type_test.rb

@@ -0,0 +1,54 @@
+require "test_helper"
+
+class ULID::Rails::Type::DataTest < Minitest::Test
+  def test_has_26_valid_characters
+    id = "01BX5ZZKBKACTAV9WEVGEMMVRZ"
+
+    assert ULID::Rails::Type::Data.valid_ulid?(id)
+  end
+
+  def test_length_less_than_26
+    id = "A" * 25
+
+    refute ULID::Rails::Type::Data.valid_ulid?(id)
+  end
+
+  def test_length_greater_than_26
+    id = "A" * 27
+
+    refute ULID::Rails::Type::Data.valid_ulid?(id)
+  end
+
+  # Crockford's Base32 is used as shown. This alphabet excludes
+  # the letters I, L, O, and U to avoid confusion and abuse.
+  # https://github.com/ulid/spec#encoding
+  def test_has_invalid_characters
+    invalid_characters = %w[I L O U]
+
+    invalid_characters.each do |char|
+      id = char * 26
+
+      refute ULID::Rails::Type::Data.valid_ulid?(id)
+    end
+  end
+
+  # The first character in a ULID must be 0, 7, or in between.
+  # Anything larger than 7, and the id would not fit into 16 bytes.
+  def test_does_not_exceed_16_bytes
+    valid_first_characters = ("0".."7").to_a
+
+    valid_first_characters.each do |char|
+      id = "#{char}#{"A" * 25}"
+
+      assert ULID::Rails::Type::Data.valid_ulid?(id)
+    end
+
+    invalid_first_characters = ("8".."9").to_a + ("A".."Z").to_a
+
+    invalid_first_characters.each do |char|
+      id = "#{char}#{"A" * 25}"
+
+      refute ULID::Rails::Type::Data.valid_ulid?(id)
+    end
+  end
+end