diff --git a/test/io/runtests.jl b/test/io/runtests.jl
new file mode 100644
index 0000000..86eb75d
--- /dev/null
+++ b/test/io/runtests.jl
@@ -0,0 +1,8 @@
+# SPDX-FileCopyrightText: 2015-2026 Jukka Aho
+# SPDX-License-Identifier: MIT
+
+using Test
+
+@testset "I/O (VTK export)" begin
+    include("test_writevtk.jl")
+end
diff --git a/test/io/test_writevtk.jl b/test/io/test_writevtk.jl
new file mode 100644
index 0000000..89757e4
--- /dev/null
+++ b/test/io/test_writevtk.jl
@@ -0,0 +1,58 @@
+# SPDX-FileCopyrightText: 2015-2026 Jukka Aho
+# SPDX-License-Identifier: MIT
+
+using Test
+using JuliaFEM
+using WriteVTK
+using Tensors: Vec
+
+@testset "write_vtu_mesh stub for non-mesh second argument" begin
+    @test_throws ErrorException write_vtu_mesh("x", 1.0)
+end
+
+@testset "write_vtu_mesh Hex8 + point/cell data" begin
+    mesh = create_structured_box_mesh(Hex8; xmin = 0.0, xmax = 1.0, nx = 2, ymin = 0.0, ymax = 1.0, ny = 1, zmin = 0.0, zmax = 1.0, nz = 1)
+    d = mktempdir()
+    base = joinpath(d, "hex8_out")
+    n = nnodes_total(mesh)
+    ne = nelements(mesh)
+    u = randn(3, n)
+    p = collect(1.0:n)
+    path = write_vtu_mesh(
+        base,
+        mesh;
+        point_data = (; displacement = u, pressure = p),
+        cell_data = (; elem_id = collect(1.0:ne)),
+    )
+    @test endswith(path, ".vtu")
+    @test isfile(path)
+end
+
+@testset "write_vtu_mesh strips .vtu suffix" begin
+    mesh = create_structured_box_mesh(Hex8; xmin = 0.0, xmax = 1.0, nx = 1, ymin = 0.0, ymax = 1.0, ny = 1, zmin = 0.0, zmax = 1.0, nz = 1)
+    d = mktempdir()
+    path = write_vtu_mesh(joinpath(d, "with_suffix.vtu"), mesh)
+    @test isfile(path)
+    @test occursin("with_suffix.vtu", path)
+end
+
+@testset "write_vtu_mesh Quad4" begin
+    mesh = create_structured_box_mesh(Quad4; xmin = 0.0, xmax = 1.0, nx = 2, ymin = 0.0, ymax = 1.0, ny = 2)
+    d = mktempdir()
+    path = write_vtu_mesh(joinpath(d, "quad"), mesh; point_data = (; s = zeros(Float64, nnodes_total(mesh))))
+    @test isfile(path)
+end
+
+@testset "write_vtu_mesh unsupported topology" begin
+    nodes10 = Vec{3,Float64}[
+        Vec(0.0, 0.0, 0.0), Vec(1.0, 0.0, 0.0), Vec(0.0, 1.0, 0.0), Vec(0.0, 0.0, 1.0),
+        Vec(0.5, 0.0, 0.0), Vec(0.5, 0.5, 0.0), Vec(0.0, 0.5, 0.0),
+        Vec(0.0, 0.0, 0.5), Vec(0.5, 0.0, 0.5), Vec(0.0, 0.5, 0.5),
+    ]
+    conn = NTuple{10,UInt32}[
+        ntuple(i -> UInt32(i), 10),
+    ]
+    mesh = Mesh{10,Tet10}(nodes10, conn)
+    d = mktempdir()
+    @test_throws ArgumentError write_vtu_mesh(joinpath(d, "t10"), mesh)
+end