add continuity test

tests/regression/test_tensor_elements.py

@@ -0,0 +1,39 @@
+from firedrake import *
+import pytest
+
+
+rg = RandomGenerator(PCG64(seed=1))
+
+
+@pytest.fixture(params=("square", "cube"))
+def mesh(request):
+    if request.param == "square":
+        return UnitSquareMesh(2, 2)
+    elif request.param == "cube":
+        return UnitCubeMesh(2, 2, 2)
+    else:
+        raise ValueError("Unrecognized mesh type")
+
+
+@pytest.mark.parametrize("degree", (0, 1, 2))
+@pytest.mark.parametrize("family", ("Regge", "HHJ"))
+def test_tensor_continuity(mesh, family, degree):
+    V = FunctionSpace(mesh, family, degree)
+    u = rg.beta(V, 1.0, 2.0)
+
+    dim = mesh.topological_dimension()
+    n = FacetNormal(mesh)
+
+    space = V.ufl_element().sobolev_space
+    if space == HDivDiv:
+        utrace = dot(n, dot(u, n))
+    elif space == HEin:
+        if dim == 2:
+            t = dot(as_matrix([[0, -1], [1, 0]]), n)
+            utrace = dot(t, dot(u, t))
+        else:
+            t = as_matrix([[0, n[2], -n[1]], [-n[2], 0, n[0]], [n[1], -n[0], 0]])
+            utrace = dot(t, dot(u, t.T))
+
+    ujump = utrace('+') - utrace('-')
+    assert assemble(inner(ujump, ujump)*dS) < 1E-10