fix test_slate_infrastructure array bounds

tests/slate/test_slate_infrastructure.py

@@ -1,6 +1,7 @@
 import pytest
 from firedrake import *
 from firedrake.formmanipulation import ExtractSubBlock
+import math
 
 
 @pytest.fixture(scope='module', params=[interval, triangle, quadrilateral])
@@ -58,23 +59,32 @@ def stiffness(function_space):
 @pytest.fixture
 def load(function_space):
     f = Function(function_space)
-    f.interpolate(Expression("cos(x[0]*pi*2)"))
+    x = SpatialCoordinate(function_space.mesh())
+    f.interpolate(cos(x[0])*math.pi*2)
     v = TestFunction(function_space)
     return Tensor(f * v * dx)
 
 
 @pytest.fixture
 def boundary_load(function_space):
     f = Function(function_space)
-    f.interpolate(Expression("cos(x[1]*pi*2)"))
+    x = SpatialCoordinate(function_space.mesh())
+    if function_space.mesh().cell_dimension() == 1:
+        f.interpolate(cos(x[0]*math.pi*2))
+    else:
+        f.interpolate(cos(x[1] * math.pi*2))
     v = TestFunction(function_space)
     return Tensor(f * v * ds)
 
 
 @pytest.fixture
 def zero_rank_tensor(function_space):
     c = Function(function_space)
-    c.interpolate(Expression("x[0]*x[1]"))
+    x = SpatialCoordinate(function_space.mesh())
+    if function_space.mesh().cell_dimension() == 1:
+        c.interpolate(x[0]*x[0])
+    else:
+        c.interpolate(x[0]*x[1])
     return Tensor(c * dx)