add test for image sampling

test/Manifest.toml

+# This file is machine-generated - editing it directly is not advised
+
+[[Base64]]
+uuid = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"
+
+[[InteractiveUtils]]
+deps = ["Markdown"]
+uuid = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
+
+[[Logging]]
+uuid = "56ddb016-857b-54e1-b83d-db4d58db5568"
+
+[[Markdown]]
+deps = ["Base64"]
+uuid = "d6f4376e-aef5-505a-96c1-9c027394607a"
+
+[[Random]]
+deps = ["Serialization"]
+uuid = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
+
+[[Serialization]]
+uuid = "9e88b42a-f829-5b0c-bbe9-9e923198166b"
+
+[[Test]]
+deps = ["InteractiveUtils", "Logging", "Random", "Serialization"]
+uuid = "8dfed614-e22c-5e08-85e1-65c5234f0b40"

test/Project.toml

+[deps]
+Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
+Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"

test/runtests.jl

+import Random
+using Test
+
+using SemiSmoothNewton
+
+Random.seed!(0)
+
+@testset "imaging" begin
+    img = rand(3, 3)
+    mesh = init_grid(img)
+
+    @test ndims_domain(mesh) == 2
+    @test ndims_space(mesh) == 2
+
+    v0 = minimum(mesh.vertices, dims = 2) |> vec
+    v1 = maximum(mesh.vertices, dims = 2) |> vec
+
+    @test v0 == [1., 1.]
+    @test v1 == [3., 3.]
+
+    f_space = FeSpace(mesh, P1(), (1,))
+    f = FeFunction(f_space)
+
+    interpolate!(f, x -> interpolate_bilinear(img, x))
+    img_sampled = sample(f)
+
+    @test img == img_sampled
+end