Tests for UTF-8 String#ljust and String#rjust

mrbgems/mruby-string-ext/test/string.rb

@@ -433,6 +433,7 @@ end
 assert('String#ljust') do
   assert_equal "hello", "hello".ljust(4)
   assert_equal "hello               ", "hello".ljust(20)
+  assert_equal 20, "hello".ljust(20).length
   assert_equal "hello123412341234123", "hello".ljust(20, '1234')
   assert_equal "hello", "hello".ljust(-3)
 end
@@ -440,10 +441,39 @@ end
 assert('String#rjust') do
   assert_equal "hello", "hello".rjust(4)
   assert_equal "               hello", "hello".rjust(20)
+  assert_equal 20, "hello".rjust(20).length
   assert_equal "123412341234123hello", "hello".rjust(20, '1234')
   assert_equal "hello", "hello".rjust(-3)
 end
 
+if UTF8STRING
+  assert('String#ljust with UTF8') do
+    assert_equal "helloん              ", "helloん".ljust(20)
+    assert_equal "helloó                            ", "helloó".ljust(34)
+    assert_equal 34, "helloó".ljust(34).length
+    assert_equal "helloんんんんんんんんんんんんんん", "hello".ljust(19, 'ん')
+    assert_equal "helloんんんんんんんんんんんんんんん", "hello".ljust(20, 'ん')
+  end
+
+  assert('String#rjust with UTF8') do
+    assert_equal "              helloん", "helloん".rjust(20)
+    assert_equal "                            helloó", "helloó".rjust(34)
+    # assert_equal 34, "helloó".rjust(34).length
+    assert_equal "んんんんんんんんんんんんんんhello", "hello".rjust(19, 'ん')
+    assert_equal "んんんんんんんんんんんんんんんhello", "hello".rjust(20, 'ん')
+  end
+
+  assert('UTF8 byte counting') do
+    skip('string length is broken after []=')
+
+    # based on assert_equal 34, "helloó".rjust(34).length
+    ret = '                                  '
+    ret[-6..-1] = "helloó"
+    
+    assert_equal 34, ret.length
+  end
+end
+
 assert('String#ljust should not change string') do
   a = "hello"
   a.ljust(20)