[Tests] add test cases from test262

See tc39/test262#3661

test/tests.js

@@ -14,7 +14,15 @@ var replacementChar = '\uFFFD';
 
 module.exports = function (toWellFormed, t) {
 	t.test('well-formed strings', function (st) {
-		forEach(v.nonStrings.concat(v.strings, wholePoo), function (value) {
+		forEach(v.nonStrings.concat(
+			v.strings,
+			wholePoo, // a concatenated surrogate pair
+			'abc', // a latin-1 string
+			'a💩c', // a surrogate pair using a literal code point
+			'a\uD83D\uDCA9c', // a surrogate pair formed by escape sequences
+			'a' + leadingPoo + trailingPoo + 'd', // a surrogate pair formed by concatenation
+			'a\u25A8c' // a non-ASCII character
+		), function (value) {
 			if (value != null) { // eslint-disable-line eqeqeq
 				var string = typeof value === 'symbol' ? SymbolDescriptiveString(value) : String(value);
 				st.equal(
@@ -29,16 +37,21 @@ module.exports = function (toWellFormed, t) {
 	});
 
 	t.test('not well-formed strings', function (st) {
-		st.equal(
-			toWellFormed(leadingPoo),
-			replacementChar,
-			'a string with a leading surrogate but no trailing surrogate has the lone surrogate replaced as expected'
-		);
-		st.equal(
-			toWellFormed(trailingPoo),
-			replacementChar,
-			'a string with a trailing surrogate but no leading surrogate has the lone surrogate replaced as expected'
-		);
+		forEach([
+			[leadingPoo, replacementChar, 'a string with a leading surrogate but no trailing surrogate'],
+			[trailingPoo, replacementChar, 'a string with a trailing surrogate but no leading surrogate'],
+			['a' + leadingPoo + 'c' + leadingPoo + 'e', 'a' + replacementChar + 'c' + replacementChar + 'e', 'leading lone surrogates'],
+			['a' + trailingPoo + 'c' + trailingPoo + 'e', 'a' + replacementChar + 'c' + replacementChar + 'e', 'trailing lone surrogates'],
+			['a' + trailingPoo + leadingPoo + 'd', 'a' + replacementChar + replacementChar + 'd', 'a wrong-ordered surrogate pair'],
+			[wholePoo.slice(0, 1), replacementChar, 'a surrogate pair sliced to the leading surrogate'],
+			[wholePoo.slice(1), replacementChar, 'a surrogate pair sliced to the trailing surrogate is not well-formed']
+		], function (arr) {
+			var str = arr[0];
+			var exp = arr[1];
+			var msg = arr[2];
+
+			st.equal(toWellFormed(str), exp, msg + ' is not well-formed, and lone surrogates are replaced as expected');
+		});
 
 		st.end();
 	});