test(stellar): add Stellar MEMO_TEXT byte length clamping and MEMO_ID bounds specs

tests/wave13_stellar_memo_sanitizer_test.py

@@ -0,0 +1,31 @@
+import unittest
+
+class TestWave13StellarMemoSanitizer(unittest.TestCase):
+    def test_stellar_text_memo_byte_length_clamping(self):
+        max_memo_bytes = 28 # Stellar MEMO_TEXT max length
+
+        def sanitize_memo(text: str) -> str:
+            encoded = text.encode('utf-8')
+            if len(encoded) <= max_memo_bytes:
+                return text
+            return encoded[:max_memo_bytes].decode('utf-8', errors='ignore')
+
+        valid_memo = "BountyGrid Wave 13"
+        self.assertEqual(sanitize_memo(valid_memo), valid_memo)
+
+        long_memo = "This is an extremely long transaction memo text that exceeds 28 bytes"
+        sanitized = sanitize_memo(long_memo)
+        self.assertTrue(len(sanitized.encode('utf-8')) <= 28)
+
+    def test_memo_id_uint64_bounds(self):
+        max_uint64 = (1 << 64) - 1
+
+        def is_valid_memo_id(num: int) -> bool:
+            return 0 <= num <= max_uint64
+
+        self.assertTrue(is_valid_memo_id(123456789))
+        self.assertFalse(is_valid_memo_id(-1))
+        self.assertFalse(is_valid_memo_id(max_uint64 + 1))
+
+if __name__ == '__main__':
+    unittest.main()