Add test coverage for parse_edid

src/tests/test_tools.py

@@ -5,12 +5,13 @@
 from __future__ import annotations
 
 import io
+import struct
 from pathlib import Path
 from typing import TYPE_CHECKING
 
 import pytest
 
-from mss.tools import to_png
+from mss.tools import parse_edid, to_png
 
 if TYPE_CHECKING:
     from collections.abc import Callable
@@ -57,3 +58,112 @@ def test_output_raw_bytes() -> None:
     raw = to_png(data, (WIDTH, HEIGHT))
     assert isinstance(raw, bytes)
     assert_is_valid_png(raw=raw)
+
+
+# ---------------------------------------------------------------------------
+# Helpers and tests for parse_edid
+# ---------------------------------------------------------------------------
+
+
+def _make_edid(
+    *,
+    manufacturer: str = "TST",
+    product_code: int = 0x1234,
+    serial_number: int = 0,
+    manufacture_week: int = 0,
+    manufacture_year: int = 30,
+    descriptors: list[tuple[int, int, str]] | None = None,
+    bad_checksum: bool = False,
+) -> bytes:
+    """Build a minimal 128-byte EDID block."""
+    data = bytearray(128)
+    data[0:8] = b"\x00\xff\xff\xff\xff\xff\xff\x00"
+    packed = ((ord(manufacturer[0]) - ord("@")) << 10) | ((ord(manufacturer[1]) - ord("@")) << 5) | (ord(manufacturer[2]) - ord("@"))
+    data[8] = (packed >> 8) & 0xFF
+    data[9] = packed & 0xFF
+    struct.pack_into("<H", data, 10, product_code)
+    struct.pack_into("<I", data, 12, serial_number)
+    data[16] = manufacture_week
+    data[17] = manufacture_year
+    data[18] = 1  # EDID version
+    data[19] = 4  # EDID revision
+    _text_len = 13  # descriptor text field is 13 bytes (slice(5, 18))
+    if descriptors:
+        for offset, tag, text in descriptors:
+            # bytes at relative offsets 0,1,2,4 must be 0 (already 0 from init)
+            data[offset + 3] = tag
+            encoded = text.encode("ascii")
+            if len(encoded) < _text_len:
+                encoded = encoded + b"\n" + b" " * (_text_len - len(encoded) - 1)
+            data[offset + 5 : offset + 18] = encoded[:_text_len]
+    checksum = (-sum(data[:127])) % 256
+    data[127] = (checksum + 1) % 256 if bad_checksum else checksum
+    return bytes(data)
+
+
+def test_parse_edid_too_short() -> None:
+    assert parse_edid(b"") == {}
+    assert parse_edid(b"\x00" * 64) == {}
+    assert parse_edid(b"\x00" * 127) == {}
+
+
+def test_parse_edid_invalid_checksum() -> None:
+    assert parse_edid(_make_edid(bad_checksum=True)) == {}
+
+
+def test_parse_edid_invalid_header() -> None:
+    data = bytearray(_make_edid())
+    data[0] = 0x01  # corrupt the header magic
+    data[127] = (-sum(data[:127])) % 256  # recompute checksum
+    assert parse_edid(bytes(data)) == {}
+
+
+def test_parse_edid_basic() -> None:
+    result = parse_edid(_make_edid(manufacturer="TST", product_code=0x1234))
+    assert result["id_legacy"] == "TST1234"
+
+
+def test_parse_edid_manufacture_year_only() -> None:
+    result = parse_edid(_make_edid(manufacture_week=0, manufacture_year=30))
+    assert result["manufacture_year"] == 2020
+    assert "manufacture_week" not in result
+    assert "model_year" not in result
+
+
+def test_parse_edid_manufacture_week_and_year() -> None:
+    result = parse_edid(_make_edid(manufacture_week=10, manufacture_year=30))
+    assert result["manufacture_year"] == 2020
+    assert result["manufacture_week"] == 10
+    assert "model_year" not in result
+
+
+def test_parse_edid_model_year() -> None:
+    result = parse_edid(_make_edid(manufacture_week=0xFF, manufacture_year=31))
+    assert result["model_year"] == 2021
+    assert "manufacture_year" not in result
+    assert "manufacture_week" not in result
+
+
+def test_parse_edid_serial_number_integer() -> None:
+    result = parse_edid(_make_edid(serial_number=12345))
+    assert result["serial_number"] == 12345
+
+
+def test_parse_edid_serial_number_not_set() -> None:
+    result = parse_edid(_make_edid(serial_number=0))
+    assert "serial_number" not in result
+
+
+def test_parse_edid_descriptor_serial_number() -> None:
+    result = parse_edid(_make_edid(descriptors=[(0x48, 0xFF, "SN123456")]))
+    assert result["serial_number"] == "SN123456"
+
+
+def test_parse_edid_descriptor_display_name() -> None:
+    result = parse_edid(_make_edid(descriptors=[(0x5A, 0xFC, "Test Monitor")]))
+    assert result["display_name"] == "Test Monitor"
+
+
+def test_parse_edid_descriptor_string_serial_overrides_integer() -> None:
+    result = parse_edid(_make_edid(serial_number=99, descriptors=[(0x48, 0xFF, "STRSERIAL")]))
+    assert result["serial_number"] == "STRSERIAL"