--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/SbpOperators/volumeops/volume_operator_test.jl	Wed Mar 17 20:34:40 2021 +0100
@@ -0,0 +1,122 @@
+using Test
+
+using Sbplib.SbpOperators
+using Sbplib.Grids
+
+import Sbplib.SbpOperators.Stencil
+import Sbplib.SbpOperators.volume_operator
+import Sbplib.SbpOperators.odd
+import Sbplib.SbpOperators.even
+
+@testset "VolumeOperator" begin
+    inner_stencil = CenteredStencil(1/4, 2/4, 1/4)
+    closure_stencils = (Stencil(1/2, 1/2; center=1), Stencil(0.,1.; center=2))
+    g_1D = EquidistantGrid(11,0.,1.)
+    g_2D = EquidistantGrid((11,12),(0.,0.),(1.,1.))
+    g_3D = EquidistantGrid((11,12,10),(0.,0.,0.),(1.,1.,1.))
+    @testset "Constructors" begin
+        @testset "1D" begin
+            op = VolumeOperator(inner_stencil,closure_stencils,(11,),even)
+            @test op == VolumeOperator(g_1D,inner_stencil,closure_stencils,even)
+            @test op == volume_operator(g_1D,inner_stencil,closure_stencils,even,1)
+            @test op isa TensorMapping{T,1,1} where T
+        end
+        @testset "2D" begin
+            op_x = volume_operator(g_2D,inner_stencil,closure_stencils,even,1)
+            op_y = volume_operator(g_2D,inner_stencil,closure_stencils,even,2)
+            Ix = IdentityMapping{Float64}((11,))
+            Iy = IdentityMapping{Float64}((12,))
+            @test op_x == VolumeOperator(inner_stencil,closure_stencils,(11,),even)⊗Iy
+            @test op_y == Ix⊗VolumeOperator(inner_stencil,closure_stencils,(12,),even)
+            @test op_x isa TensorMapping{T,2,2} where T
+            @test op_y isa TensorMapping{T,2,2} where T
+        end
+        @testset "3D" begin
+            op_x = volume_operator(g_3D,inner_stencil,closure_stencils,even,1)
+            op_y = volume_operator(g_3D,inner_stencil,closure_stencils,even,2)
+            op_z = volume_operator(g_3D,inner_stencil,closure_stencils,even,3)
+            Ix = IdentityMapping{Float64}((11,))
+            Iy = IdentityMapping{Float64}((12,))
+            Iz = IdentityMapping{Float64}((10,))
+            @test op_x == VolumeOperator(inner_stencil,closure_stencils,(11,),even)⊗Iy⊗Iz
+            @test op_y == Ix⊗VolumeOperator(inner_stencil,closure_stencils,(12,),even)⊗Iz
+            @test op_z == Ix⊗Iy⊗VolumeOperator(inner_stencil,closure_stencils,(10,),even)
+            @test op_x isa TensorMapping{T,3,3} where T
+            @test op_y isa TensorMapping{T,3,3} where T
+            @test op_z isa TensorMapping{T,3,3} where T
+        end
+    end
+
+    @testset "Sizes" begin
+        @testset "1D" begin
+            op = volume_operator(g_1D,inner_stencil,closure_stencils,even,1)
+            @test range_size(op) == domain_size(op) == size(g_1D)
+        end
+
+        @testset "2D" begin
+            op_x = volume_operator(g_2D,inner_stencil,closure_stencils,even,1)
+            op_y = volume_operator(g_2D,inner_stencil,closure_stencils,even,2)
+            @test range_size(op_y) == domain_size(op_y) ==
+                  range_size(op_x) == domain_size(op_x) == size(g_2D)
+        end
+        @testset "3D" begin
+            op_x = volume_operator(g_3D,inner_stencil,closure_stencils,even,1)
+            op_y = volume_operator(g_3D,inner_stencil,closure_stencils,even,2)
+            op_z = volume_operator(g_3D,inner_stencil,closure_stencils,even,3)
+            @test range_size(op_z) == domain_size(op_z) ==
+                  range_size(op_y) == domain_size(op_y) ==
+                  range_size(op_x) == domain_size(op_x) == size(g_3D)
+        end
+    end
+
+    op_x = volume_operator(g_2D,inner_stencil,closure_stencils,even,1)
+    op_y = volume_operator(g_2D,inner_stencil,closure_stencils,odd,2)
+    v = zeros(size(g_2D))
+    Nx = size(g_2D)[1]
+    Ny = size(g_2D)[2]
+    for i = 1:Nx
+        v[i,:] .= i
+    end
+    rx = copy(v)
+    rx[1,:] .= 1.5
+    rx[Nx,:] .= (2*Nx-1)/2
+    ry = copy(v)
+    ry[:,Ny-1:Ny] = -v[:,Ny-1:Ny]
+
+    @testset "Application" begin
+        @test op_x*v ≈ rx rtol = 1e-14
+        @test op_y*v ≈ ry rtol = 1e-14
+    end
+
+    @testset "Regions" begin
+        @test (op_x*v)[Index(1,Lower),Index(3,Interior)] ≈ rx[1,3] rtol = 1e-14
+        @test (op_x*v)[Index(2,Lower),Index(3,Interior)] ≈ rx[2,3] rtol = 1e-14
+        @test (op_x*v)[Index(6,Interior),Index(3,Interior)] ≈ rx[6,3] rtol = 1e-14
+        @test (op_x*v)[Index(10,Upper),Index(3,Interior)] ≈ rx[10,3] rtol = 1e-14
+        @test (op_x*v)[Index(11,Upper),Index(3,Interior)] ≈ rx[11,3] rtol = 1e-14
+
+        @test_throws BoundsError (op_x*v)[Index(3,Lower),Index(3,Interior)]
+        @test_throws BoundsError (op_x*v)[Index(9,Upper),Index(3,Interior)]
+
+        @test (op_y*v)[Index(3,Interior),Index(1,Lower)] ≈ ry[3,1] rtol = 1e-14
+        @test (op_y*v)[Index(3,Interior),Index(2,Lower)] ≈ ry[3,2] rtol = 1e-14
+        @test (op_y*v)[Index(3,Interior),Index(6,Interior)] ≈ ry[3,6] rtol = 1e-14
+        @test (op_y*v)[Index(3,Interior),Index(11,Upper)] ≈ ry[3,11] rtol = 1e-14
+        @test (op_y*v)[Index(3,Interior),Index(12,Upper)] ≈ ry[3,12] rtol = 1e-14
+
+        @test_throws BoundsError (op_y*v)[Index(3,Interior),Index(10,Upper)]
+        @test_throws BoundsError (op_y*v)[Index(3,Interior),Index(3,Lower)]
+    end
+
+    @testset "Inferred" begin
+        @inferred apply(op_x, v,1,1)
+        @inferred apply(op_x, v, Index(1,Lower),Index(1,Lower))
+        @inferred apply(op_x, v, Index(6,Interior),Index(1,Lower))
+        @inferred apply(op_x, v, Index(11,Upper),Index(1,Lower))
+
+        @inferred apply(op_y, v,1,1)
+        @inferred apply(op_y, v, Index(1,Lower),Index(1,Lower))
+        @inferred apply(op_y, v, Index(1,Lower),Index(6,Interior))
+        @inferred apply(op_y, v, Index(1,Lower),Index(11,Upper))
+    end
+end