fix: file a slug-platform bios under its own system

tests/test_system_ids.py

@@ -0,0 +1,57 @@
+"""A machine has one system id in the profiles, and a file goes to its own.
+
+picodrive filed the Mega CD as sega-segacd and fbneo the disk system as
+nes-fds, where every other profile and every platform says sega-megacd and
+nintendo-fds. On RomM, which keeps firmware per system folder, picodrive's
+Mega CD BIOS went to gamegear/, the first of its systems, and fbneo's
+channelf.zip and SNES DSP sets to colecovision/.
+"""
+
+from __future__ import annotations
+
+import sys
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+sys.path.insert(0, str(REPO_ROOT / "scripts"))
+
+from common import SYSTEM_ALIASES, load_emulator_profiles  # noqa: E402
+from packextras import _slug_for  # noqa: E402
+
+
+class ProfilesSpellEachMachineOnce(unittest.TestCase):
+    def test_no_profile_uses_an_alias_spelling(self):
+        profiles = load_emulator_profiles(str(REPO_ROOT / "emulators"))
+        found = sorted(
+            f"{name}: {sid}"
+            for name, profile in profiles.items()
+            for sid in [
+                *profile.get("systems", []),
+                *(f.get("system") for f in profile.get("files", []) if f.get("system")),
+            ]
+            if str(sid).lower() in SYSTEM_ALIASES
+        )
+        self.assertEqual(sorted(set(found)), [])
+
+
+class AFileGoesToItsOwnSystemFolder(unittest.TestCase):
+    PROFILES = {"picodrive": {"systems": ["sega-game-gear", "sega-megacd"]}}
+    SYSTEMS = {"sega-game-gear", "sega-mega-cd"}
+    NORM = {"gamegear": "sega-game-gear", "megacd": "sega-mega-cd"}
+    SLUGS = {"sega-game-gear": "gamegear", "sega-mega-cd": "segacd"}
+
+    def slug(self, entry):
+        return _slug_for(entry, self.PROFILES, self.SYSTEMS, self.NORM, self.SLUGS)
+
+    def test_the_entry_system_decides(self):
+        self.assertEqual(
+            self.slug({"profile": "picodrive", "system": "sega-megacd"}), "segacd"
+        )
+
+    def test_without_one_the_emulator_systems_decide(self):
+        self.assertEqual(self.slug({"profile": "picodrive"}), "gamegear")
+
+
+if __name__ == "__main__":
+    unittest.main()