Raise ArgumentError if attempting to transliterate anything that is not a string

activesupport/lib/active_support/inflector/transliterate.rb

@@ -57,6 +57,8 @@ module Inflector
     #   transliterate('Jürgen')
     #   # => "Juergen"
     def transliterate(string, replacement = "?".freeze)
+      raise ArgumentError, "Can only transliterate strings. Received #{string.class.name}" unless string.is_a?(String)
+
       I18n.transliterate(ActiveSupport::Multibyte::Unicode.normalize(
         ActiveSupport::Multibyte::Unicode.tidy_bytes(string), :c),
           replacement: replacement)

activesupport/test/transliterate_test.rb

@@ -31,4 +31,22 @@ def test_transliterate_should_work_with_custom_i18n_rules_and_uncomposed_utf8
   def test_transliterate_should_allow_a_custom_replacement_char
     assert_equal "a*b", ActiveSupport::Inflector.transliterate("a索b", "*")
   end
+
+  def test_transliterate_handles_empty_string
+    assert_equal "", ActiveSupport::Inflector.transliterate("")
+  end
+
+  def test_transliterate_handles_nil
+    exception = assert_raises ArgumentError do
+      ActiveSupport::Inflector.transliterate(nil)
+    end
+    assert_equal "Can only transliterate strings. Received NilClass", exception.message
+  end
+
+  def test_transliterate_handles_unknown_object
+    exception = assert_raises ArgumentError do
+      ActiveSupport::Inflector.transliterate(Object.new)
+    end
+    assert_equal "Can only transliterate strings. Received Object", exception.message
+  end
 end