diff --git a/tests/jerry/string-prototype-charat.js b/tests/jerry/string-prototype-charat.js
index 25f06da52..92d0c71ee 100644
--- a/tests/jerry/string-prototype-charat.js
+++ b/tests/jerry/string-prototype-charat.js
@@ -45,6 +45,15 @@ assert("hello world!".charAt(11) === "!");
 
 assert("hello world!".charAt(12) === "");
 
+// check unicode
+assert("hello\u000B\u000C\u0020\u00A0world!".charAt(8) === "\u00A0");
+
+assert("hello\uD834\uDF06world!".charAt(6) === "\uDF06");
+
+assert("hell\u006F\u006F w\u006F\u006Frld!".charAt(8) === "\u006F");
+
+assert("\u00A9\u006F".charAt(2) === "");
+
 // check negative
 assert("hello world!".charAt(-1) === "");
 
diff --git a/tests/jerry/string-prototype-charcodeat.js b/tests/jerry/string-prototype-charcodeat.js
index 97fc80786..8e10ff262 100644
--- a/tests/jerry/string-prototype-charcodeat.js
+++ b/tests/jerry/string-prototype-charcodeat.js
@@ -44,6 +44,15 @@ assert("hello world!".charCodeAt(11) === 33);
 
 assert(isNaN("hello world!".charCodeAt(12)));
 
+// check unicode
+assert("hello\u000B\u000C\u0020\u00A0world!".charCodeAt(8) === 160);
+
+assert("hello\uD834\uDF06world!".charCodeAt(6) === 57094);
+
+assert("hell\u006F\u006F w\u006F\u006Frld!".charCodeAt(8) === 111);
+
+assert(isNaN("\u00A9\u006F".charCodeAt(2)));
+
 // check negative
 assert(isNaN("hello world!".charCodeAt(-1)));
 
diff --git a/tests/jerry/string-prototype-concat.js b/tests/jerry/string-prototype-concat.js
index 7a890f844..4eb117bf3 100644
--- a/tests/jerry/string-prototype-concat.js
+++ b/tests/jerry/string-prototype-concat.js
@@ -29,6 +29,12 @@ assert("Hello ".concat(s1) === "Hello Hello ");
 
 assert(s1.concat(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9) === "Hello 012345678901234567890123456789");
 
+assert("".concat() === "");
+
+// check unicode
+assert("\u0041".concat("\u0041", "\u1041") === "\u0041\u0041\u1041");
+assert("\u0041\u1D306A".concat("\u0041", "\u1041") === "\u0041\u1D306A\u0041\u1041");
+
 // check undefined
 var y;
 assert("Check ".concat(y) === "Check undefined");