diff --git a/test/test_2d.jl b/test/test_2d.jl
index 93bf176..d8838aa 100644
--- a/test/test_2d.jl
+++ b/test/test_2d.jl
@@ -23,7 +23,7 @@ end
     @timed_testset "mesh data" begin
       # create the output file to be tested
       @test_nowarn trixi2vtk(joinpath(outdir, "mesh_" * LEADING_ZEROS * "000010.h5"), output_directory=outdir)
-      outfilename = "mesh_000010_celldata.vtu"
+      outfilename = "mesh_" * LEADING_ZEROS * "000010_celldata.vtu"
       out_file = joinpath(outdir, outfilename)
 
       # save output file to `artifacts` to facilitate debugging of failing tests
@@ -39,7 +39,7 @@ end
     @timed_testset "solution celldata" begin
       # create the output file to be tested
       @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000010.h5"), output_directory=outdir)
-      outfilename = "solution_000010_celldata.vtu"
+      outfilename = "solution_" * LEADING_ZEROS * "000010_celldata.vtu"
       out_file = joinpath(outdir, outfilename)
 
       # save output file to `artifacts` to facilitate debugging of failing tests
@@ -55,7 +55,7 @@ end
     @timed_testset "reinterpolate with nonuniform data with VTU format" begin
       # Create and test output with reinterpolation (default options: `reinterpolate=true, data_is_uniform=false`)
       @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000010.h5"), output_directory=outdir)
-      outfilename = "solution_000010.vtu"
+      outfilename = "solution_" * LEADING_ZEROS * "000010.vtu"
       out_file = joinpath(outdir, outfilename)
 
       # save output file to `artifacts` to facilitate debugging of failing tests
@@ -71,7 +71,7 @@ end
     @timed_testset "reinterpolate with nonuniform data with VTI format" begin
       # Create and test output with reinterpolation (default options: `reinterpolate=true, data_is_uniform=false`)
       @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000010.h5"), output_directory=outdir, format=:vti)
-      outfilename = "solution_000010.vti"
+      outfilename = "solution_" * LEADING_ZEROS * "000010.vti"
       out_file = joinpath(outdir, outfilename)
 
       # save output file to `artifacts` to facilitate debugging of failing tests
@@ -87,7 +87,7 @@ end
     @timed_testset "do not reinterpolate with nonuniform data" begin
       # Create and test output without reinterpolation on LGL nodes
       @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000010.h5"), output_directory=outdir, reinterpolate=false)
-      outfilename = "solution_000010.vtu"
+      outfilename = "solution_" * LEADING_ZEROS * "000010.vtu"
       out_file = joinpath(outdir, outfilename)
 
       # save output file to `artifacts` to facilitate debugging of failing tests
@@ -104,7 +104,7 @@ end
       # Create and test output without reinterpolation on uniform nodes
       # OBS! This is a dummy test just to exercise code. The resulting plot will look weird.
       @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000010.h5"), output_directory=outdir, reinterpolate=false, data_is_uniform=true)
-      outfilename = "solution_000010.vtu"
+      outfilename = "solution_" * LEADING_ZEROS * "000010.vtu"
       out_file = joinpath(outdir, outfilename)
 
       # save output file to `artifacts` to facilitate debugging of failing tests
@@ -154,7 +154,7 @@ end
         #      that only needs to be tested once.
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_00000*.h5"), output_directory=outdir)
 
-        outfilename = "solution_000001_celldata.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000001_celldata.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -170,7 +170,7 @@ end
       @timed_testset "reinterpolate with nonuniform data" begin
         # Create and test output with reinterpolation (default options: `reinterpolate=true, data_is_uniform=false`)
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000001.h5"), output_directory=outdir)
-        outfilename = "solution_000001.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000001.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -186,7 +186,7 @@ end
       @timed_testset "do not reinterpolate with nonuniform data" begin
         # Create and test output without reinterpolation on LGL nodes
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000001.h5"), output_directory=outdir, reinterpolate=false)
-        outfilename = "solution_000001.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000001.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -203,7 +203,7 @@ end
         # Create and test output without reinterpolation on uniform nodes
         # OBS! This is a dummy test just to exercise code. The resulting plot will look weird.
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000001.h5"), output_directory=outdir, reinterpolate=false, data_is_uniform=true)
-        outfilename = "solution_000001.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000001.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -246,7 +246,7 @@ end
       @timed_testset "solution celldata" begin
         # create the output file to be tested
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000001.h5"), output_directory=outdir)
-        outfilename = "solution_000001_celldata.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000001_celldata.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -262,7 +262,7 @@ end
       @timed_testset "reinterpolate with nonuniform data" begin
         # Create and test output with reinterpolation (default options: `reinterpolate=true, data_is_uniform=false`)
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000001.h5"), output_directory=outdir)
-        outfilename = "solution_000001.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000001.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -278,7 +278,7 @@ end
       @timed_testset "do not reinterpolate with nonuniform data" begin
         # Create and test output without reinterpolation on LGL nodes
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000001.h5"), output_directory=outdir, reinterpolate=false)
-        outfilename = "solution_000001.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000001.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -295,7 +295,7 @@ end
         # Create and test output without reinterpolation on uniform nodes
         # OBS! This is a dummy test just to exercise code. The resulting plot will look weird.
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000001.h5"), output_directory=outdir, reinterpolate=false, data_is_uniform=true)
-        outfilename = "solution_000001.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000001.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -316,7 +316,7 @@ end
       @timed_testset "mesh data" begin
         # create the output file to be tested
         @test_nowarn trixi2vtk(joinpath(outdir, "mesh_" * LEADING_ZEROS * "000005.h5"), output_directory=outdir)
-        outfilename = "mesh_000005_celldata.vtu"
+        outfilename = "mesh_" * LEADING_ZEROS * "000005_celldata.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -332,7 +332,7 @@ end
       @timed_testset "solution celldata" begin
         # create the output file to be tested
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000005.h5"), output_directory=outdir)
-        outfilename = "solution_000005_celldata.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000005_celldata.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -348,7 +348,7 @@ end
       @timed_testset "reinterpolate with nonuniform data" begin
         # Create and test output with reinterpolation (default options: `reinterpolate=true, data_is_uniform=false`)
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000005.h5"), output_directory=outdir)
-        outfilename = "solution_000005.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000005.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -364,7 +364,7 @@ end
       @timed_testset "do not reinterpolate with nonuniform data" begin
         # Create and test output without reinterpolation on LGL nodes
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000005.h5"), output_directory=outdir, reinterpolate=false)
-        outfilename = "solution_000005.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000005.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests
@@ -381,7 +381,7 @@ end
         # Create and test output without reinterpolation on uniform nodes
         # OBS! This is a dummy test just to exercise code. The resulting plot will look weird.
         @test_nowarn trixi2vtk(joinpath(outdir, "solution_" * LEADING_ZEROS * "000005.h5"), output_directory=outdir, reinterpolate=false, data_is_uniform=true)
-        outfilename = "solution_000005.vtu"
+        outfilename = "solution_" * LEADING_ZEROS * "000005.vtu"
         out_file = joinpath(outdir, outfilename)
 
         # save output file to `artifacts` to facilitate debugging of failing tests