Handle nil inputs in Sanitize::Rails::Engine#clean and #clean!

lib/sanitize/rails.rb

@@ -51,13 +51,13 @@ def cleaner
     # means that text passed through `Sanitize::Rails::Engine.clean`
     # will not be escaped by ActionView's XSS filtering utilities.
     def clean(string)
-      ::ActiveSupport::SafeBuffer.new string.dup.tap { |s| clean!(s) }
+      ::ActiveSupport::SafeBuffer.new string.to_s.dup.tap { |s| clean!(s) }
     end
 
     # Sanitizes the given `string` in place and does NOT mark it as `html_safe`
     #
     def clean!(string)
-      cleaner.clean!(string)
+      cleaner.clean!(string.to_s).to_s
     end
 
     def callback_for(options) #:nodoc:

test/sanitize_rails_engine_test.rb

@@ -5,7 +5,7 @@
 require 'sanitize/rails'
 
 # Test suite for Sanitize::Rails::Engine
-class SanitizeRailsEngineTest < MiniTest::Unit::TestCase
+class SanitizeRailsEngineTest < Minitest::Test
   def setup
     @engine = Sanitize::Rails::Engine
   end
@@ -50,4 +50,12 @@ def test_clean_returns_safe_buffers
     new_string = @engine.clean string
     assert_instance_of ::ActiveSupport::SafeBuffer, new_string
   end
+
+  def test_clean_returns_blank_string_for_nil_input
+    assert_equal '', @engine.clean(nil)
+  end
+
+  def test_clean_bang_returns_blank_string_for_nil_input
+    assert_equal '', @engine.clean!(nil)
+  end
 end

test/sanitize_rails_string_extension_test.rb

@@ -5,7 +5,7 @@
 require 'sanitize/rails'
 
 # Test suite for Sanitize::Rails::Engine
-class SanitizeRailsStringExtensionTest < MiniTest::Unit::TestCase
+class SanitizeRailsStringExtensionTest < Minitest::Test
   SanitizableString = Class.new(String) { include Sanitize::Rails::String }
 
   def setup

test/test_helper.rb

@@ -1,2 +1 @@
-require 'minitest/unit'
 require 'minitest/autorun'