--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/ext/sparse_array_kit_test.jl	Tue Sep 10 21:59:10 2024 +0200
@@ -0,0 +1,35 @@
+using Test
+
+using Diffinitive
+using Diffinitive.Grids
+using Diffinitive.SbpOperators
+
+using SparseArrayKit
+using Tokens
+using Tullio
+
+
+@testset "SparseArray" begin
+    g = equidistant_grid((0,0),(1,2), 20,30)
+    stencil_set = read_stencil_set(sbp_operators_path()*"standard_diagonal.toml"; order=4)
+
+
+    @testset let Δ = laplace(g, stencil_set), M = SparseArray(Δ)
+        @test ndims(M) == 4
+        @test size(M) == (20,30,20,30)
+
+        v = rand(size(g)...)
+        @tullio Mv[i,j] := M[i,j,k,l]*v[k,l]
+
+        @test Mv ≈ Δ*v
+    end
+
+    @testset let dₙ = normal_derivative(g, stencil_set,CartesianBoundary{1,LowerBoundary}()), M = SparseArray(dₙ)
+        @test ndims(M) == 3
+        @test size(M) == (30,20,30)
+
+        v = rand(size(g)...)
+        @tullio Mv[i] := M[i,j,k]*v[j,k]
+        @test Mv ≈ dₙ*v
+    end
+end