Refactor test_from_FAST: extend fixture to 2 years, remove separate regression test

The test fixture FAST_test_tracks.nc now has year=[2025,2026] (only
seeds_per_month is extended; track variables retain their n_trk dim).
The existing len(tc_track.data)==5 assertion now acts as the regression
check: the buggy year-loop code would return 5x2=10 tracks.

The separate test_from_FAST_not_multiplied_by_year_dim (with its
temporary-file scaffolding) is removed.

Author: Simona Meiler

climada/hazard/test/data/FAST_test_tracks.nc

@@ -19,7 +19,6 @@
 Test tc_tracks module.
 """
 
-import tempfile
 import unittest
 from datetime import datetime as dt
 
@@ -661,8 +660,13 @@ def test_from_simulations_storm(self):
         self.assertEqual(len(tc_track.data), 0)
 
     def test_from_FAST(self):
-        """test the correct import of netcdf files from FAST model and the conversion to a
-        different xr.array structure compatible with CLIMADA."""
+        """Test the correct import of netcdf files from FAST model and the conversion to a
+        different xr.array structure compatible with CLIMADA.
+
+        The test fixture contains 5 tracks across 2 years. The regression check
+        ``len(tc_track.data) == 5`` ensures that tracks are not multiplied by the
+        ``year`` dimension (the bug would produce 5 × 2 = 10 tracks instead).
+        """
 
         tc_track = tc.TCTracks.from_FAST(TEST_TRACK_FAST)
 
@@ -705,70 +709,6 @@ def test_from_FAST(self):
         self.assertEqual(tc_track.data[0].environmental_pressure.data[0], 1010)
         self.assertEqual(tc_track.data[0].basin[0], "NA")
 
-    def test_from_FAST_not_multiplied_by_year_dim(self):
-        """Regression test: FAST tracks must not be repeated across `year` dimension."""
-        with tempfile.TemporaryDirectory() as tmpdir:
-            ds = xr.Dataset(
-                {
-                    "lon_trks": (
-                        ("n_trk", "time"),
-                        np.array(
-                            [
-                                [290.0, 291.0, 292.0],
-                                [300.0, 301.0, 302.0],
-                            ],
-                            dtype=float,
-                        ),
-                    ),
-                    "lat_trks": (
-                        ("n_trk", "time"),
-                        np.array(
-                            [
-                                [10.0, 10.5, 11.0],
-                                [15.0, 15.5, 16.0],
-                            ],
-                            dtype=float,
-                        ),
-                    ),
-                    "vmax_trks": (
-                        ("n_trk", "time"),
-                        np.array(
-                            [
-                                [20.0, 21.0, 22.0],
-                                [25.0, 26.0, 27.0],
-                            ],
-                            dtype=float,
-                        ),
-                    ),
-                    "tc_month": ("n_trk", np.array([8, 9], dtype=np.int64)),
-                    "tc_basins": ("n_trk", np.array(["NA", "NA"], dtype="<U2")),
-                    "tc_years": ("n_trk", np.array([1998, 1999], dtype=np.int64)),
-                    "seeds_per_month": (
-                        ("year", "basin", "month"),
-                        np.zeros((4, 1, 12), dtype=float),
-                    ),
-                },
-                coords={
-                    "n_trk": ("n_trk", np.array([0, 1], dtype=np.int64)),
-                    "time": ("time", np.array([0, 10800, 21600], dtype=float)),
-                    "year": (
-                        "year",
-                        np.array([1998, 1999, 2000, 2001], dtype=np.int64),
-                    ),
-                    "basin": ("basin", np.array(["NA"], dtype="<U2")),
-                    "month": ("month", np.arange(1, 13, dtype=np.int64)),
-                },
-            )
-
-            path = DATA_DIR.joinpath(tmpdir, "fast_regression.nc")
-            ds.to_netcdf(path)
-
-            tc_track = tc.TCTracks.from_FAST(DATA_DIR.joinpath(tmpdir))
-
-            self.assertEqual(tc_track.size, 2)
-            self.assertEqual(tc_track.data[0].time.dt.year.values[0], 1998)
-            self.assertEqual(tc_track.data[1].time.dt.year.values[0], 1999)
-
     def test_to_geodataframe_points(self):
         """Conversion of TCTracks to GeoDataFrame using Points."""
         tc_track = tc.TCTracks.from_processed_ibtracs_csv(TEST_TRACK)