fix low level issues

tests/test_sport.py

@@ -1,4 +1,4 @@
-from bincio.extract.sport import normalise_sport
+from bincio.extract.sport import normalise_sport, normalise_sub_sport
 
 
 def test_cycling_variants():
@@ -14,3 +14,22 @@ def test_running_variants():
 def test_unknown_falls_back_to_other():
     assert normalise_sport("yoga") == "other"
     assert normalise_sport(None) == "other"
+
+
+def test_sub_sport_strava_camelcase():
+    assert normalise_sub_sport("MountainBikeRide") == "mountain"
+    assert normalise_sub_sport("GravelRide") == "gravel"
+    assert normalise_sub_sport("VirtualRide") == "indoor"
+    assert normalise_sub_sport("Ride") == "road"
+
+
+def test_sub_sport_ski_variants():
+    assert normalise_sub_sport("AlpineSki") == "alpine"
+    assert normalise_sub_sport("NordicSki") == "nordic"
+    assert normalise_sub_sport("BackcountrySki") == "nordic"
+
+
+def test_sub_sport_unknown_returns_none():
+    assert normalise_sub_sport("yoga") is None
+    assert normalise_sub_sport(None) is None
+    assert normalise_sub_sport("generic") is None