diff --git a/tests/testthat/test-export_prj.R b/tests/testthat/test-export_prj.R
index c49bf688fd5cc421c028db0b7a2ed42c3d146789..51ee0905596aefa4e7791ee7181654d38847a902 100644
--- a/tests/testthat/test-export_prj.R
+++ b/tests/testthat/test-export_prj.R
@@ -8,7 +8,6 @@ test_that("export_prj works", {
 
     # Define prj_path and OGS6 object, then read in .prj file
     ogs6_obj <- OGS6$new(sim_name = "flow_free_expansion",
-                         sim_id = 1,
                          sim_path = test_path)
 
 
diff --git a/tests/testthat/test-ogs6.R b/tests/testthat/test-ogs6.R
index 9b1d820f55493d9bb55a959746d767fff6e7bb2a..d18113e9800fb184e3fe052ce7d525b3ad9e9902 100644
--- a/tests/testthat/test-ogs6.R
+++ b/tests/testthat/test-ogs6.R
@@ -5,7 +5,6 @@ test_that("OGS6$clear() works as expected", {
 
     ogs6_obj <- OGS6$new(
         sim_name = "sim",
-        sim_id = 1,
         sim_path = "sim_path")
 
     ogs6_obj$add(r2ogs6_parameter(
@@ -24,7 +23,6 @@ test_that("OGS6$add() works", {
 
     ogs6_obj <- OGS6$new(
         sim_name = "sim",
-        sim_id = 1,
         sim_path = "sim_path")
 
     ogs6_obj$add(r2ogs6_parameter(
diff --git a/tests/testthat/test-ogs6_ensemble.R b/tests/testthat/test-ogs6_ensemble.R
index 9c90c510fa632a18809c5e9993a43d0ccd90f78a..304af142e39dc4e06b20cac82847b3c6d388c5f1 100644
--- a/tests/testthat/test-ogs6_ensemble.R
+++ b/tests/testthat/test-ogs6_ensemble.R
@@ -5,7 +5,6 @@ test_that("OGS6_Ensemble initialization works", {
 
     ogs6_obj <- OGS6$new(
         sim_name = "sim",
-        sim_id = 1,
         sim_path = "sim_path")
 
     ogs6_obj$add(r2ogs6_parameter(
diff --git a/tests/testthat/test-gml.R b/tests/testthat/test-ogs6_gml.R
similarity index 85%
rename from tests/testthat/test-gml.R
rename to tests/testthat/test-ogs6_gml.R
index 1840cb0b4125175641693edeaa75d1efe25d4d05..e3536f7002fecb1f2dc0d8860ce230cecc306e83 100644
--- a/tests/testthat/test-gml.R
+++ b/tests/testthat/test-ogs6_gml.R
@@ -1,3 +1,17 @@
+
+
+test_that("OGS6_gml initialization works", {
+
+    gml <- OGS6_gml$new(name = "my_gml",
+                        points = tibble::tibble(x = c(0, 0),
+                                                y = c(1, 1),
+                                                z = c(0, 1)),
+                        polylines = list(list("my_line", c(1, 0, 1))))
+
+    expect_equal(length(gml$points), 3)
+})
+
+
 test_that("validate_points works", {
 
     point_list <- list(x = c(0, 0), y = c(1, 1), z = c(0, 1))
@@ -66,4 +80,4 @@ test_that("validate_surfaces works", {
     expect_error(validate_surfaces(surface_tibble))
 
     #...(WIP)
-})
\ No newline at end of file
+})
diff --git a/tests/testthat/test-ogs6_pvd.R b/tests/testthat/test-ogs6_pvd.R
new file mode 100644
index 0000000000000000000000000000000000000000..8aa68814d6aac8fba51936700186d962bca4ad9d
--- /dev/null
+++ b/tests/testthat/test-ogs6_pvd.R
@@ -0,0 +1,97 @@
+
+
+test_that("OGS6_pvd initialization works", {
+
+    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
+                            "flow_no_strain.pvd",
+                            package = "r2ogs6")
+
+    ogs6_pvd <- OGS6_pvd$new(pvd_path)
+
+    expect_equal(length(ogs6_pvd$vtu_paths), 2)
+    expect_equal(ogs6_pvd$vtu_paths[[1]],
+                 "flow_no_strain_ts_0_t_0.000000.vtu")
+    expect_equal(ogs6_pvd$vtu_paths[[2]],
+                 "flow_no_strain_ts_1000_t_100.000000.vtu")
+})
+
+
+test_that("OGS6_pvd$get_timestep_by_vtu_path works", {
+
+    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
+                            "flow_no_strain.pvd",
+                            package = "r2ogs6")
+
+    ogs6_pvd <- OGS6_pvd$new(pvd_path)
+
+    vtu_path <- "flow_no_strain_ts_1000_t_100.000000.vtu"
+
+    timestep <- ogs6_pvd$timestep_by_vtu(vtu_path = vtu_path)
+
+    expect_equal(timestep, 99.9999999999986)
+})
+
+
+test_that("OGS6_pvd$get_point_data_at works", {
+
+    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
+                            "flow_no_strain.pvd",
+                            package = "r2ogs6")
+
+    ogs6_pvd <- OGS6_pvd$new(pvd_path)
+
+
+    tbl_from_id <- ogs6_pvd$get_point_data(0,
+                                           keys = c("epsilon_xx",
+                                                     "epsilon_xy"))
+
+    # Test for DataArray where NumberOfComponents == 1
+    tbl_from_coords <- ogs6_pvd$get_point_data_at(coordinates = c(0, 0, 0),
+                                                  keys = c("epsilon_xx",
+                                                            "epsilon_xy"))
+
+    expect_equal(tbl_from_coords$epsilon_xx, tbl_from_id$epsilon_xx)
+    expect_equal(tbl_from_coords$epsilon_xy, tbl_from_id$epsilon_xy)
+})
+
+
+test_that("OGS6_pvd$get_point_data works", {
+
+    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
+                            "flow_no_strain.pvd",
+                            package = "r2ogs6")
+
+    ogs6_pvd <- OGS6_pvd$new(pvd_path)
+
+    # Test for DataArray where NumberOfComponents == 1
+    tbl_simple <- ogs6_pvd$get_point_data(point_ids = c(0, 1, 2),
+                                          keys = c("epsilon_xx",
+                                                    "epsilon_xy"))
+
+    expect_equal(nrow(tbl_simple), 6)
+
+    # Test for DataArray where NumberOfComponents(displacement) == 2
+    tbl_nocomp <- ogs6_pvd$get_point_data(point_ids = c(0, 1, 2),
+                                          keys = c("displacement",
+                                                    "epsilon_xx"))
+
+    expect_equal(nrow(tbl_nocomp), 6)
+})
+
+
+test_that("OGS6_pvd$get_cell_data works", {
+
+    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
+                            "flow_no_strain.pvd",
+                            package = "r2ogs6")
+
+    ogs6_pvd <- OGS6_pvd$new(pvd_path)
+
+    # Test for DataArray where NumberOfComponents(displacement) == 2
+    tbl_nocomp <- ogs6_pvd$get_cell_data(
+        cell_ids = c(0, 1, 2),
+        keys = c("permeability",
+                  "principal_stress_values"))
+
+    expect_equal(nrow(tbl_nocomp), 6)
+})
diff --git a/tests/testthat/test-vtu.R b/tests/testthat/test-ogs6_vtu.R
similarity index 54%
rename from tests/testthat/test-vtu.R
rename to tests/testthat/test-ogs6_vtu.R
index 91326498dd6c9a0ff833ef5a1dd0738e1c9a8006..84e052081f2d1823bace1fc0df7ae6f124e5ec3c 100644
--- a/tests/testthat/test-vtu.R
+++ b/tests/testthat/test-ogs6_vtu.R
@@ -13,106 +13,6 @@ skip_if_python_modules_missing <- function() {
 }
 
 
-#===== OGS6_pvd =====
-
-
-test_that("OGS6_pvd initialization works", {
-
-    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
-                            "flow_no_strain.pvd",
-                            package = "r2ogs6")
-
-    ogs6_pvd <- OGS6_pvd$new(pvd_path)
-
-    expect_equal(length(ogs6_pvd$vtu_paths), 2)
-    expect_equal(ogs6_pvd$vtu_paths[[1]],
-                 "flow_no_strain_ts_0_t_0.000000.vtu")
-    expect_equal(ogs6_pvd$vtu_paths[[2]],
-                 "flow_no_strain_ts_1000_t_100.000000.vtu")
-})
-
-
-test_that("OGS6_pvd$get_timestep_by_vtu_path works", {
-
-    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
-                            "flow_no_strain.pvd",
-                            package = "r2ogs6")
-
-    ogs6_pvd <- OGS6_pvd$new(pvd_path)
-
-    vtu_path <- "flow_no_strain_ts_1000_t_100.000000.vtu"
-
-    timestep <- ogs6_pvd$timestep_by_vtu(vtu_path = vtu_path)
-
-    expect_equal(timestep, 99.9999999999986)
-})
-
-
-test_that("OGS6_pvd$get_point_data_at works", {
-
-    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
-                            "flow_no_strain.pvd",
-                            package = "r2ogs6")
-
-    ogs6_pvd <- OGS6_pvd$new(pvd_path)
-
-
-    tbl_from_id <- ogs6_pvd$get_point_data(0,
-                                           Names = c("epsilon_xx",
-                                                     "epsilon_xy"))
-
-    # Test for DataArray where NumberOfComponents == 1
-    tbl_from_coords <- ogs6_pvd$get_point_data_at(coordinates = c(0, 0, 0),
-                                                  Names = c("epsilon_xx",
-                                                            "epsilon_xy"))
-
-    expect_equal(tbl_from_coords$epsilon_xx, tbl_from_id$epsilon_xx)
-    expect_equal(tbl_from_coords$epsilon_xy, tbl_from_id$epsilon_xy)
-})
-
-
-test_that("OGS6_pvd$get_point_data works", {
-
-    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
-                            "flow_no_strain.pvd",
-                            package = "r2ogs6")
-
-    ogs6_pvd <- OGS6_pvd$new(pvd_path)
-
-    # Test for DataArray where NumberOfComponents == 1
-    tbl_simple <- ogs6_pvd$get_point_data(point_ids = c(0, 1, 2),
-                                          Names = c("epsilon_xx",
-                                                    "epsilon_xy"))
-
-    expect_equal(nrow(tbl_simple), 6)
-
-    # Test for DataArray where NumberOfComponents(displacement) == 2
-    tbl_nocomp <- ogs6_pvd$get_point_data(point_ids = c(0, 1, 2),
-                                          Names = c("displacement",
-                                                    "epsilon_xx"))
-
-    expect_equal(nrow(tbl_nocomp), 6)
-})
-
-
-test_that("OGS6_pvd$get_cell_data works", {
-
-    pvd_path <- system.file("extdata/benchmarks/flow_no_strain",
-                            "flow_no_strain.pvd",
-                            package = "r2ogs6")
-
-    ogs6_pvd <- OGS6_pvd$new(pvd_path)
-
-    # Test for DataArray where NumberOfComponents(displacement) == 2
-    tbl_nocomp <- ogs6_pvd$get_cell_data(
-        cell_ids = c(0, 1, 2),
-        Names = c("permeability",
-                  "principal_stress_values"))
-
-    expect_equal(nrow(tbl_nocomp), 6)
-})
-
-
 #===== OGS6_vtu =====
 
 
@@ -169,13 +69,13 @@ test_that("OGS6_vtu$get_point_data_at() works", {
     vtu_obj <- OGS6_vtu$new(vtu_path = vtu_path)
 
     tbl <- vtu_obj$get_point_data_at(c(0.01, 0, 0),
-                                     Names = "epsilon_xx")
+                                     keys = "epsilon_xx")
     expect_equal(tbl$epsilon_xx, 3.282899e-15)
 
 
     bigger_tbl <- vtu_obj$get_point_data_at(list(c(0.01, 0, 0),
                                                  c(0.42, 0, 0)),
-                                            Names = "epsilon_xx")
+                                            keys = "epsilon_xx")
     expect_equal(bigger_tbl$epsilon_xx[[2]], 1.233661e-16)
 })
 
diff --git a/tests/testthat/test-read_in_prj.R b/tests/testthat/test-read_in_prj.R
index 8acb7b2315c417037d21b169513caba192676279..69613515b1e29f760443078a35aadee59eb2f9a2 100644
--- a/tests/testthat/test-read_in_prj.R
+++ b/tests/testthat/test-read_in_prj.R
@@ -6,7 +6,6 @@ test_that("read_in works for process objects", {
                              "flow_free_expansion.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in(ogs6_obj,
@@ -31,7 +30,6 @@ test_that("read_in works for medium objects", {
                              "flow_free_expansion.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in(ogs6_obj,
@@ -48,7 +46,6 @@ test_that("read_in works for time_loop objects", {
                              "flow_free_expansion.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in(ogs6_obj,
@@ -68,7 +65,6 @@ test_that("read_in works for parameter objects", {
                              "flow_free_expansion.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in(ogs6_obj,
@@ -87,7 +83,6 @@ test_that("read_in works for process_variable objects", {
                              "flow_free_expansion.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in(ogs6_obj,
@@ -103,7 +98,6 @@ test_that("read_in works for nonlinear_solver objects", {
                              "flow_free_expansion.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in(ogs6_obj,
@@ -125,7 +119,6 @@ test_that("read_in works for linear_solver objects", {
                              "flow_free_expansion.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in(ogs6_obj,
@@ -146,7 +139,6 @@ test_that("read_in works with newline value separation", {
                              "liakopoulos.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in(ogs6_obj,
@@ -167,7 +159,6 @@ test_that("read_in_prj works for processes/include tags", {
                              "circle_1e1_axi.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in_prj(ogs6_obj,
@@ -185,7 +176,6 @@ test_that("read_in_prj works for EmbeddedFracturePermeability/cube.prj", {
                              "cube.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in_prj(ogs6_obj,
diff --git a/tests/testthat/test-read_in_utils.R b/tests/testthat/test-read_in_utils.R
index 699aef8faa322aeb97c7d5758fd755bce3adefd1..d0e8f4c5d3d64a6b2111bb51c98614bfdc410d58 100644
--- a/tests/testthat/test-read_in_utils.R
+++ b/tests/testthat/test-read_in_utils.R
@@ -6,7 +6,6 @@ test_that("node_to_object works for simple r2ogs6 classes", {
                              "flow_free_expansion.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "sim",
-                         sim_id = 1,
                          sim_path = "sim_path")
 
     read_in(ogs6_obj, prj_path, "/OpenGeoSysProject/parameters/parameter")
diff --git a/tests/testthat/test-sim_utils.R b/tests/testthat/test-sim_utils.R
index 91741ee9a508604c23ff038e745dd8d9e32cdd17..32ce99f2ad8d227690a5f8b5d3ada08a0045c8ed 100644
--- a/tests/testthat/test-sim_utils.R
+++ b/tests/testthat/test-sim_utils.R
@@ -62,7 +62,6 @@ test_that("ogs_export_sim_files works", {
                              "circle_1e1_axi.prj", package = "r2ogs6"))
 
     ogs6_obj <- OGS6$new(sim_name = "circle_1e1_axi",
-                         sim_id = 1,
                          sim_path = test_path)
 
     read_in_prj(ogs6_obj,