Fix tests for the case when CUDA is available on the system

tests/metatensor/test_workflow_metatensor.py

@@ -94,7 +94,9 @@ def system(self, device=None, dtype=None):
             properties=mts_torch.Labels.range("distance", 1),
         )
 
-        return system.to(device=device), neighbors.to(device=device)
+        return system.to(device=device, dtype=dtype), neighbors.to(
+            device=device, dtype=dtype
+        )
 
     def check_operation(self, calculator, device, dtype):
         """Make sure computation runs and returns a metatensor.TensorMap."""
@@ -107,12 +109,16 @@ def check_operation(self, calculator, device, dtype):
 
     def test_operation_as_python(self, CalculatorClass, params, device, dtype):
         """Run `check_operation` as a normal python script"""
-        calculator = CalculatorClass(**params)
+        params["potential"].device = device
+        params["potential"].dtype = dtype
+        calculator = CalculatorClass(**params, device=device, dtype=dtype)
         self.check_operation(calculator=calculator, device=device, dtype=dtype)
 
     def test_operation_as_torch_script(self, CalculatorClass, params, device, dtype):
         """Run `check_operation` as a compiled torch script module."""
-        calculator = CalculatorClass(**params)
+        params["potential"].device = device
+        params["potential"].dtype = dtype
+        calculator = CalculatorClass(**params, device=device, dtype=dtype)
         scripted = torch.jit.script(calculator)
         self.check_operation(calculator=scripted, device=device, dtype=dtype)