Comment 5 for bug 844642

Sample test case:

class FormOperations(unittest.TestCase):

    def test_lhs_rhs_simple(self):
        # Test taking lhs/rhs of forms involving constants. Most else
        # should be testable in UFL itself.

        mesh = UnitSquare(2, 2)
        V = FunctionSpace(mesh, "CG", 1)
        f = Constant(1.0)
        v = TestFunction(V)
        u = TrialFunction(V)

        F = inner(grad(f*v), grad(u))*dx + f*v*dx
        a, L = system(F)

        assert(len(a._integrals) == 1)
        assert(len(L._integrals) == 1)