diff --git a/test/data_for_test.py b/test/data_for_test.py
index 18cd5eac873d23f8937a76659f0fcd630b995d04..558bf33bf3ac6e5636841f0857e2537410f4635d 100644
--- a/test/data_for_test.py
+++ b/test/data_for_test.py
@@ -27,7 +27,7 @@ class FluxDataSingle:
 
         self.state_pair = self.swap_array_rows(
                 u.transposed_array_from_string(states_str), self.dir_internal)
-        self.states = u.expand_to_6(self.state_pair)
+        self.states = u.expand_to_n(self.state_pair, 6)
 
         # FIXME: these should be generalized fluxes
         # FIXME: make a clear distinction between fluxes in physical and
@@ -108,7 +108,7 @@ class FluxDataVector:
         self.fluxes = self.fill_transverse_with_halo(
                 u.expand_to_n(flux_pair, self.nxhalo))
 
-        identity = np.identity(self.ndim, dtype=float64, order="F")
+        identity = np.identity(self.ndim, dtype=np.float64).copy(order="F")
         self.metrics = np.empty((self.ndim, self.ndim,
                 self.nxhalo, self.nyhalo, self.nzhalo))
         for i in range(self.nxhalo):
diff --git a/test/test_eigensystem.py b/test/test_eigensystem.py
index 4b0a7a6b14af212778076242e3e0fbef81e7f2e7..de37e8959b697457e314844613f4f6f68c5f49ff 100644
--- a/test/test_eigensystem.py
+++ b/test/test_eigensystem.py
@@ -83,7 +83,8 @@ def test_lax_wavespeeds(
 
     nvars = 5
 
-    lam_pointwise = u.expand_to_6(u.transposed_array_from_string(lam_pointwise_str))
+    lam_pointwise = u.expand_to_n(
+            u.transposed_array_from_string(lam_pointwise_str), 6)
     lam_roe = u.array_from_string(lam_roe_str)
     lam_dev = u.empty_array_on_device(queue, nvars)
 
diff --git a/test/test_flux_derivatives.py b/test/test_flux_derivatives.py
index b768625863e0e4d2ba7887a3d90a8474eedd653b..f506f85dda0a73cd20c90a3774133cb1ff6c423d 100644
--- a/test/test_flux_derivatives.py
+++ b/test/test_flux_derivatives.py
@@ -17,10 +17,10 @@ from pyopencl.tools import (  # noqa
 import utilities as u
 from data_for_test import (  # noqa: F401
         cfd_test_data_fixture
-        vector_data as vd
         )
 
 
+@pytest.mark.slow
 def test_compute_flux_derivatives_uniform_grid(ctx_factory, cfd_test_data_fixture):
     data = cfd_test_data_fixture