Set time as float in test

Co-authored-by: Erik van Sebille <e.vansebille@uu.nl>

Author: fluidnumericsJoe

tests/test_uxarray_fieldset.py

@@ -123,7 +123,7 @@ def test_fesom2_square_delaunay_uniform_z_coordinate_eval():
     fieldset = FieldSet([UVW, P, UVW.U, UVW.V, UVW.W])
 
     assert np.isclose(
-        fieldset.U.eval(time=ds.time[0].values, z=[1.0], y=[30.0], x=[30.0], applyConversion=False),
+        fieldset.U.eval(time=[0.], z=[1.0], y=[30.0], x=[30.0], applyConversion=False),
         1.0,
         rtol=1e-3,
         atol=1e-6,