encoding.utf8 fixes

vlib/encoding/utf8/utf8_util_test.v

@@ -1,9 +1,28 @@
 import encoding.utf8
 
 fn test_utf8_util() {
-	src:="ăĂ ôÔ testo 怔"
+
+	// string test
+	src:="ăĂ ôÔ testo 怔"//_\u1E5A\u1E5B<=>\u1F49\u1F41<=>\u0128\u012a\u012c" // len 29 runes, raw 49 bytes
+	src_upper:="ĂĂ ÔÔ TESTO Æ€”"//_\u1E5A\u1E5A<=>\u1F49\u1F49<=>\u0128\u012A\u012C"
+	src_lower:="ăă ôô testo 怔"//_\u1E5B\u1E5B<=>\u1F41\u1F41<=>\u0129\u012B\u012D"
 	upper:=utf8.to_upper(src)
 	lower:=utf8.to_lower(src)
-	assert upper=="ĂĂ ÔÔ TESTO Æ€”"
-	assert lower=="ăă ôô testo 怔"
+	assert upper==src_upper
+	assert lower==src_lower
+
+	// ustring test
+	src1:=src.ustring()
+	upper1:=utf8.u_to_upper(src1)
+	lower1:=utf8.u_to_lower(src1)
+	assert upper1==( src_upper.ustring() )
+	assert lower1==( src_lower.ustring() )
+
+	// test len function
+	assert utf8.len("pippo")==5
+	assert utf8.len(src)==15 //29
+	assert src.len==24 //49
+	// test u_len function
+	assert utf8.u_len(src1)==15 //29
+	assert utf8.u_len("pippo".ustring())==5
 }