diff --git a/src/util/test/string-utf8.c b/src/util/test/string-utf8.c
new file mode 100644
index 000000000..2f208538b
--- /dev/null
+++ b/src/util/test/string-utf8.c
@@ -0,0 +1,132 @@
+/* Copyright (c) 2013-2022 Jeffrey Pfau
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "util/test/suite.h"
+
+#include <mgba-util/string.h>
+
+M_TEST_DEFINE(strlenASCII) {
+    assert_int_equal(utf8strlen(""), 0);
+    assert_int_equal(utf8strlen("a"), 1);
+    assert_int_equal(utf8strlen("aa"), 2);
+    assert_int_equal(utf8strlen("aaa"), 3);
+}
+
+M_TEST_DEFINE(strlenMultibyte) {
+    assert_int_equal(utf8strlen("\300\200"), 1);
+    assert_int_equal(utf8strlen("a\300\200"), 2);
+    assert_int_equal(utf8strlen("\300\200a"), 2);
+    assert_int_equal(utf8strlen("a\300\200a"), 3);
+
+    assert_int_equal(utf8strlen("\300\200\300\200"), 2);
+    assert_int_equal(utf8strlen("a\300\200\300\200"), 3);
+    assert_int_equal(utf8strlen("\300\200a\300\200"), 3);
+    assert_int_equal(utf8strlen("\300\200\300\200a"), 3);
+
+    assert_int_equal(utf8strlen("\340\200\200"), 1);
+    assert_int_equal(utf8strlen("a\340\200\200"), 2);
+    assert_int_equal(utf8strlen("\340\200\200a"), 2);
+    assert_int_equal(utf8strlen("a\340\200\200a"), 3);
+
+    assert_int_equal(utf8strlen("\340\200\200\340\200\200"), 2);
+    assert_int_equal(utf8strlen("a\340\200\200\340\200\200"), 3);
+    assert_int_equal(utf8strlen("\340\200\200a\340\200\200"), 3);
+    assert_int_equal(utf8strlen("\340\200\200\340\200\200a"), 3);
+
+    assert_int_equal(utf8strlen("\340\200\200\300\200"), 2);
+    assert_int_equal(utf8strlen("\300\200\340\200\200"), 2);
+
+    assert_int_equal(utf8strlen("\360\200\200\200"), 1);
+    assert_int_equal(utf8strlen("a\360\200\200\200"), 2);
+    assert_int_equal(utf8strlen("\360\200\200\200a"), 2);
+    assert_int_equal(utf8strlen("a\360\200\200\200a"), 3);
+
+    assert_int_equal(utf8strlen("\360\200\200\200\360\200\200\200"), 2);
+    assert_int_equal(utf8strlen("a\360\200\200\200\360\200\200\200"), 3);
+    assert_int_equal(utf8strlen("\360\200\200\200a\360\200\200\200"), 3);
+    assert_int_equal(utf8strlen("\360\200\200\200\360\200\200\200a"), 3);
+
+    assert_int_equal(utf8strlen("\360\200\200\200\300\200"), 2);
+    assert_int_equal(utf8strlen("\300\200\360\200\200\200"), 2);
+
+    assert_int_equal(utf8strlen("\360\200\200\200\340\200\200"), 2);
+    assert_int_equal(utf8strlen("\340\200\200\360\200\200\200"), 2);
+}
+
+M_TEST_DEFINE(strlenDegenerate) {
+    assert_int_equal(utf8strlen("\200"), 1);
+    assert_int_equal(utf8strlen("\200a"), 2);
+
+    assert_int_equal(utf8strlen("\300"), 1);
+    assert_int_equal(utf8strlen("\300a"), 2);
+
+    assert_int_equal(utf8strlen("\300\300"), 2);
+    assert_int_equal(utf8strlen("\300\300a"), 3);
+    assert_int_equal(utf8strlen("\300\300\200"), 2);
+
+    assert_int_equal(utf8strlen("\300\200\200"), 2);
+    assert_int_equal(utf8strlen("\300\200\200a"), 3);
+
+    assert_int_equal(utf8strlen("\340"), 1);
+    assert_int_equal(utf8strlen("\340a"), 2);
+    assert_int_equal(utf8strlen("\340\300"), 2);
+    assert_int_equal(utf8strlen("\340\300a"), 3);
+    assert_int_equal(utf8strlen("\340\300\200"), 2);
+    assert_int_equal(utf8strlen("\340\200"), 1);
+    assert_int_equal(utf8strlen("\340\200a"), 2);
+    assert_int_equal(utf8strlen("\340\200\200\200"), 2);
+    assert_int_equal(utf8strlen("\340\200\200\200a"), 3);
+
+    assert_int_equal(utf8strlen("\360"), 1);
+    assert_int_equal(utf8strlen("\360a"), 2);
+    assert_int_equal(utf8strlen("\360\300"), 2);
+    assert_int_equal(utf8strlen("\360\300a"), 3);
+    assert_int_equal(utf8strlen("\360\300\200"), 2);
+    assert_int_equal(utf8strlen("\360\200"), 1);
+    assert_int_equal(utf8strlen("\360\200a"), 2);
+    assert_int_equal(utf8strlen("\360\200\300"), 2);
+    assert_int_equal(utf8strlen("\360\200\300a"), 3);
+    assert_int_equal(utf8strlen("\360\200\300\200"), 2);
+    assert_int_equal(utf8strlen("\360\200\200"), 1);
+    assert_int_equal(utf8strlen("\360\200\200a"), 2);
+
+    assert_int_equal(utf8strlen("\370"), 1);
+    assert_int_equal(utf8strlen("\370a"), 2);
+    assert_int_equal(utf8strlen("\370\200"), 2);
+    assert_int_equal(utf8strlen("\370\200a"), 3);
+    assert_int_equal(utf8strlen("\374"), 1);
+    assert_int_equal(utf8strlen("\374a"), 2);
+    assert_int_equal(utf8strlen("\374\200"), 2);
+    assert_int_equal(utf8strlen("\374\200a"), 3);
+    assert_int_equal(utf8strlen("\376"), 1);
+    assert_int_equal(utf8strlen("\376a"), 2);
+    assert_int_equal(utf8strlen("\376\200"), 2);
+    assert_int_equal(utf8strlen("\376\200a"), 3);
+    assert_int_equal(utf8strlen("\377"), 1);
+    assert_int_equal(utf8strlen("\377a"), 2);
+    assert_int_equal(utf8strlen("\377\200"), 2);
+    assert_int_equal(utf8strlen("\377\200a"), 3);
+}
+
+M_TEST_DEFINE(roundtrip) {
+    uint32_t unichar;
+    char buf[8] = {0};
+    for (unichar = 0; unichar < 0x110000; ++unichar) {
+        memset(buf, 0, sizeof(buf));
+        size_t len = toUtf8(unichar, buf) + 1;
+        const char* ptr = buf;
+        assert_true(len);
+        assert_false(buf[len]);
+        assert_int_equal(utf8Char(&ptr, &len), unichar);
+        assert_int_equal(len, 1);
+    }
+}
+
+M_TEST_SUITE_DEFINE(StringUTF8,
+    cmocka_unit_test(strlenASCII),
+    cmocka_unit_test(strlenMultibyte),
+    cmocka_unit_test(strlenDegenerate),
+    cmocka_unit_test(roundtrip),
+)