🎉 Initial commit

tests/test_mbap.py

@@ -0,0 +1,70 @@
+"""MBAP codec tests."""
+
+from __future__ import annotations
+
+import pytest
+
+from wago_sim.mbap import (
+    MBAP_HEADER_SIZE,
+    MbapError,
+    MbapFrameReader,
+    MbapHeader,
+    build_frame,
+)
+
+
+def test_header_roundtrip():
+    header = MbapHeader(transaction_id=0x1234, protocol_id=0, length=6, unit_id=1)
+    encoded = header.encode()
+    assert len(encoded) == 7
+    decoded = MbapHeader.decode(encoded + b"\x03\x00\x00\x00\x02")
+    assert decoded == header
+
+
+def test_decode_requires_complete_frame():
+    with pytest.raises(MbapError):
+        MbapHeader.decode(b"\x00\x01\x00\x00\x00\x06\x01")
+
+
+def test_protocol_id_rejected():
+    with pytest.raises(MbapError):
+        MbapHeader.decode(b"\x00\x01\x00\x01\x00\x06\x01\x03\x00\x00\x00\x02")
+
+
+def test_build_frame():
+    frame = build_frame(7, 1, b"\x03\x00\x00\x00\x02")
+    assert frame[:2] == (7).to_bytes(2, "big")
+    assert frame[4:6] == (6).to_bytes(2, "big")
+    assert frame[6] == 1
+
+
+def test_frame_reader_splits_stream():
+    reader = MbapFrameReader()
+    f1 = build_frame(1, 1, b"\x03\x00\x00\x00\x02")
+    f2 = build_frame(2, 1, b"\x01\x00\x00\x00\x08")
+    blob = f1 + f2
+    # feed an incomplete header first
+    reader.feed(blob[:5])
+    assert reader.pop_frame() is None
+    # feed through the end of frame 1 (12 bytes): it becomes complete
+    reader.feed(blob[5:12])
+    h1, p1 = reader.pop_frame()
+    assert h1.transaction_id == 1
+    assert p1 == b"\x03\x00\x00\x00\x02"
+    # frame 2 arrives in pieces
+    reader.feed(blob[12:15])
+    assert reader.pop_frame() is None
+    reader.feed(blob[15:])
+    h2, p2 = reader.pop_frame()
+    assert h2.transaction_id == 2
+    assert p2 == b"\x01\x00\x00\x00\x08"
+    assert reader.pop_frame() is None
+
+
+def test_frame_reader_rejects_bad_protocol():
+    reader = MbapFrameReader()
+    reader.feed(b"\x00\x01\xDE\xAD\x00\x06\x01\x03\x00\x00\x00\x02")
+    import pytest
+
+    with pytest.raises(MbapError):
+        reader.pop_frame()