Fix CuPy benchmark availability guard

benchmarks/benchmarks/common.py

@@ -46,7 +46,7 @@ def get_xr_dataarray(
     if type == "numpy":
         pass
     elif type == "cupy":
-        if not has_cuda_and_cupy:
+        if not has_cuda_and_cupy():
             raise NotImplementedError()
         import cupy
         z = cupy.asarray(z)

benchmarks/tests/test_common.py

@@ -0,0 +1,40 @@
+import sys
+from unittest.mock import Mock
+
+import pytest
+
+from benchmarks.benchmarks import common
+
+
+@pytest.mark.parametrize("backend", ["cupy", "dask+cupy"])
+@pytest.mark.parametrize("cupy_installed", [False, True])
+def test_gpu_benchmark_skips_when_cuda_unavailable(
+    monkeypatch, backend, cupy_installed
+):
+    available = Mock(return_value=False)
+    monkeypatch.setattr(common, "has_cuda_and_cupy", available)
+    cupy = Mock() if cupy_installed else None
+    if cupy_installed:
+        cupy.asarray.side_effect = AssertionError("must skip GPU conversion")
+    monkeypatch.setitem(sys.modules, "cupy", cupy)
+
+    with pytest.raises(NotImplementedError):
+        common.get_xr_dataarray((2, 3), backend)
+
+    available.assert_called_once_with()
+    if cupy_installed:
+        cupy.asarray.assert_not_called()
+
+
+def test_cupy_benchmark_reaches_conversion_when_cuda_available(monkeypatch):
+    available = Mock(return_value=True)
+    monkeypatch.setattr(common, "has_cuda_and_cupy", available)
+    cupy = Mock()
+    cupy.asarray.side_effect = RuntimeError("conversion reached")
+    monkeypatch.setitem(sys.modules, "cupy", cupy)
+
+    with pytest.raises(RuntimeError, match="conversion reached"):
+        common.get_xr_dataarray((2, 3), "cupy")
+
+    available.assert_called_once_with()
+    cupy.asarray.assert_called_once()