MIL-002: Step 1 - User interface

Review record RC-024 (Go, autonomous mode, not independent).

Task: MIL-002#1
Task: MIL-002#2
Task: MIL-002#3
Task: MIL-002#4

tests/unit/test_generate_images.py

@@ -0,0 +1,58 @@
+"""Tests of the image generator tool.
+
+@file test_generate_images.py
+@brief Checks the PNG files written by tools/generate_images.py.
+"""
+
+import importlib.util
+import struct
+from pathlib import Path
+from types import ModuleType
+
+import pytest
+
+from flash_card.constants import (
+    CARD_BACK_IMAGE_NAME,
+    CARD_FRONT_IMAGE_NAME,
+    CARD_HEIGHT,
+    CARD_WIDTH,
+    RIGHT_IMAGE_NAME,
+    WRONG_IMAGE_NAME,
+)
+
+_TOOL_PATH = Path(__file__).resolve().parents[2] / "tools" / "generate_images.py"
+_SIGNATURE = b"\x89PNG\r\n\x1a\n"
+
+
+def _load_tool() -> ModuleType:
+    spec = importlib.util.spec_from_file_location("generate_images", _TOOL_PATH)
+    assert spec is not None
+    assert spec.loader is not None
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+@pytest.fixture(scope="module")
+def generated(tmp_path_factory: pytest.TempPathFactory) -> Path:
+    output_dir = tmp_path_factory.mktemp("assets")
+    assert _load_tool().main(["--output-dir", str(output_dir)]) == 0
+    return output_dir
+
+
+@pytest.mark.parametrize(
+    ("name", "width", "height"),
+    [
+        (CARD_FRONT_IMAGE_NAME, CARD_WIDTH, CARD_HEIGHT),
+        (CARD_BACK_IMAGE_NAME, CARD_WIDTH, CARD_HEIGHT),
+        (RIGHT_IMAGE_NAME, 100, 100),
+        (WRONG_IMAGE_NAME, 100, 100),
+    ],
+)
+def test_generate_images_writes_png_with_expected_size(
+    generated: Path, name: str, width: int, height: int
+) -> None:
+    data = (generated / name).read_bytes()
+    assert data.startswith(_SIGNATURE)
+    assert data[12:16] == b"IHDR"
+    assert struct.unpack(">II", data[16:24]) == (width, height)