Port tl-types fromm grammers

client/tests/serializable_test.py

@@ -0,0 +1,28 @@
+from pytest import mark
+from telethon._impl.tl.core import serialize_bytes_to
+
+
+@mark.parametrize(
+    ("string", "prefix", "suffix"),
+    [
+        ("", b"\00", b"\00\x00\x00"),
+        ("Hi", b"\02", b"\00"),
+        ("Hi!", b"\03", b""),
+        ("Hello", b"\05", b"\00\x00"),
+        ("Hello, world!", b"\x0d", b"\00\x00"),
+        (
+            "This is a very long string, and it has to be longer than 253 \
+characters, which are quite a few but we can make it! Although, \
+it is quite challenging. The quick brown fox jumps over the lazy \
+fox. There is still some more text we need to type. Oh, this \
+sentence made it past!",
+            b"\xfe\x11\x01\x00",
+            b"\x00\x00\x00",
+        ),
+    ],
+)
+def test_string(string: str, prefix: bytes, suffix: bytes) -> None:
+    expected = prefix + string.encode("ascii") + suffix
+    buffer = bytearray()
+    serialize_bytes_to(buffer, string.encode("ascii"))
+    assert bytes(buffer) == expected