diff --git a/test/API/H5_api_dataset_test.c b/test/API/H5_api_dataset_test.c
index 0f78dff3c9a..1fd144ad1bb 100644
--- a/test/API/H5_api_dataset_test.c
+++ b/test/API/H5_api_dataset_test.c
@@ -9861,7 +9861,8 @@ test_dataset_vlen_io(void)
 
     /* Make sure the connector supports the API functions being tested */
     if (!(vol_cap_flags_g & H5VL_CAP_FLAG_FILE_BASIC) || !(vol_cap_flags_g & H5VL_CAP_FLAG_GROUP_BASIC) ||
-        !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_BASIC) || !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_MORE)) {
+        !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_BASIC) || !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_MORE) ||
+        !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_MORE)) {
         SKIPPED();
         printf("    API functions for basic file, group, or dataset aren't supported with this "
                "connector\n");
@@ -9955,9 +9956,6 @@ test_dataset_vlen_io(void)
 
     dset_string = H5I_INVALID_HID;
 
-    memset(wbuf, 0, sizeof(hvl_t) * DATASET_VLEN_IO_DSET_DIMS);
-    memset(rbuf, 0, sizeof(hvl_t) * DATASET_VLEN_IO_DSET_DIMS);
-
     PASSED();
 
     BEGIN_MULTIPART
@@ -9985,6 +9983,9 @@ test_dataset_vlen_io(void)
             if ((H5Dwrite(dset_int, vlen_int, space_id, H5S_ALL, H5P_DEFAULT, (const void *)wbuf)) < 0)
                 PART_TEST_ERROR(rw_all_int);
 
+            if (H5Dflush(dset_int) < 0)
+                PART_TEST_ERROR(rw_hyperslab_selection);
+
             /* Close and reopen file objects to flush cache */
             if (H5Dclose(dset_int) < 0)
                 PART_TEST_ERROR(rw_all_int);
@@ -10014,6 +10015,11 @@ test_dataset_vlen_io(void)
             if ((H5Dread(dset_int, vlen_int, space_id, H5S_ALL, H5P_DEFAULT, (void *)rbuf)) < 0)
                 PART_TEST_ERROR(rw_all_int);
 
+            /* Close to finalize read */
+            if (H5Dclose(dset_int) < 0)
+                PART_TEST_ERROR(rw_all_int);
+            dset_int = H5I_INVALID_HID;
+
             /* Verify data */
             for (size_t i = 0; i < DATASET_VLEN_IO_DSET_DIMS; i++) {
                 if (!rbuf[i].p)
@@ -10027,12 +10033,6 @@ test_dataset_vlen_io(void)
                         PART_TEST_ERROR(rw_all_int);
             }
 
-            /* Close before use in selection tests */
-            if (H5Dclose(dset_int) < 0)
-                PART_TEST_ERROR(rw_all_int);
-
-            dset_int = H5I_INVALID_HID;
-
             /* Reset buffers */
             if (H5Treclaim(vlen_int, space_id, H5P_DEFAULT, rbuf) < 0)
                 PART_TEST_ERROR(rw_all_int);
@@ -10069,6 +10069,9 @@ test_dataset_vlen_io(void)
             if ((H5Dwrite(dset_float, vlen_float, space_id, H5S_ALL, H5P_DEFAULT, (const void *)wbuf)) < 0)
                 PART_TEST_ERROR(rw_all_float);
 
+            if (H5Dflush(dset_float) < 0)
+                PART_TEST_ERROR(rw_hyperslab_selection);
+
             /* Close and reopen file objects to flush cache */
             if (H5Dclose(dset_float) < 0)
                 PART_TEST_ERROR(rw_all_float);
@@ -10098,6 +10101,11 @@ test_dataset_vlen_io(void)
             if ((H5Dread(dset_float, vlen_float, space_id, H5S_ALL, H5P_DEFAULT, (void *)rbuf)) < 0)
                 PART_TEST_ERROR(rw_all_float);
 
+            /* Close to finalize read */
+            if (H5Dclose(dset_float) < 0)
+                PART_TEST_ERROR(rw_all_float);
+            dset_float = H5I_INVALID_HID;
+
             /* Verify data */
             for (size_t i = 0; i < DATASET_VLEN_IO_DSET_DIMS; i++) {
                 if (!rbuf[i].p)
@@ -10116,7 +10124,6 @@ test_dataset_vlen_io(void)
             }
 
             /* Reset buffers */
-
             if (H5Treclaim(vlen_float, space_id, H5P_DEFAULT, rbuf) < 0)
                 PART_TEST_ERROR(rw_all_float);
 
@@ -10155,6 +10162,9 @@ test_dataset_vlen_io(void)
             if ((H5Dwrite(dset_string, vlen_string, space_id, H5S_ALL, H5P_DEFAULT, (const void *)wbuf)) < 0)
                 PART_TEST_ERROR(rw_all_string);
 
+            if (H5Dflush(dset_string) < 0)
+                PART_TEST_ERROR(rw_hyperslab_selection);
+
             /* Close and reopen file objects to flush cache */
             if (H5Dclose(dset_string) < 0)
                 PART_TEST_ERROR(rw_all_string);
@@ -10185,6 +10195,11 @@ test_dataset_vlen_io(void)
             if ((H5Dread(dset_string, vlen_string, space_id, H5S_ALL, H5P_DEFAULT, (void *)rbuf)) < 0)
                 PART_TEST_ERROR(rw_all_string);
 
+            /* Close to finalize read */
+            if (H5Dclose(dset_string) < 0)
+                PART_TEST_ERROR(rw_all_string);
+            dset_string = H5I_INVALID_HID;
+
             /* Verify data */
             for (size_t i = 0; i < DATASET_VLEN_IO_DSET_DIMS; i++) {
                 if (!rbuf[i].p)
@@ -10205,7 +10220,6 @@ test_dataset_vlen_io(void)
             }
 
             /* Reset buffers */
-
             if (H5Treclaim(vlen_string, space_id, H5P_DEFAULT, rbuf) < 0)
                 PART_TEST_ERROR(rw_all_string);
 
@@ -10251,6 +10265,9 @@ test_dataset_vlen_io(void)
             if ((H5Dwrite(dset_int, vlen_int, space_id, space_id, H5P_DEFAULT, (const void *)wbuf)) < 0)
                 PART_TEST_ERROR(rw_point_selection);
 
+            if (H5Dflush(dset_int) < 0)
+                PART_TEST_ERROR(rw_hyperslab_selection);
+
             /* Close and reopen file objects to flush cache */
             if (H5Dclose(dset_int) < 0)
                 PART_TEST_ERROR(rw_point_selection);
@@ -10277,6 +10294,11 @@ test_dataset_vlen_io(void)
             if ((H5Dread(dset_int, vlen_int, space_id, space_id, H5P_DEFAULT, (void *)rbuf)) < 0)
                 PART_TEST_ERROR(rw_point_selection);
 
+            /* Close to finalize read */
+            if (H5Dclose(dset_int) < 0)
+                PART_TEST_ERROR(rw_point_selection);
+            dset_int = H5I_INVALID_HID;
+
             /* Verify data */
             for (size_t i = 0; i < DATASET_VLEN_IO_DSET_DIMS; i++) {
                 if (i % 2 == 0) {
@@ -10299,10 +10321,6 @@ test_dataset_vlen_io(void)
                 }
             }
 
-            if (H5Dclose(dset_int) < 0)
-                PART_TEST_ERROR(rw_point_selection);
-            dset_int = H5I_INVALID_HID;
-
             /* Reset buffers */
             if (H5Treclaim(vlen_int, space_id, H5P_DEFAULT, rbuf) < 0)
                 PART_TEST_ERROR(rw_point_selection);
@@ -10349,6 +10367,9 @@ test_dataset_vlen_io(void)
             if ((H5Dwrite(dset_int, vlen_int, space_id, space_id, H5P_DEFAULT, (const void *)wbuf)) < 0)
                 PART_TEST_ERROR(rw_hyperslab_selection);
 
+            if (H5Dflush(dset_int) < 0)
+                PART_TEST_ERROR(rw_hyperslab_selection);
+
             /* Close and reopen file objects to flush cache */
             if (H5Dclose(dset_int) < 0)
                 PART_TEST_ERROR(rw_hyperslab_selection);
@@ -10375,6 +10396,11 @@ test_dataset_vlen_io(void)
             if ((H5Dread(dset_int, vlen_int, space_id, space_id, H5P_DEFAULT, (void *)rbuf)) < 0)
                 PART_TEST_ERROR(rw_hyperslab_selection);
 
+            /* Close to finalize read */
+            if (H5Dclose(dset_int) < 0)
+                PART_TEST_ERROR(rw_hyperslab_selection);
+            dset_int = H5I_INVALID_HID;
+
             /* Verify data */
             for (size_t i = 0; i < DATASET_VLEN_IO_DSET_DIMS; i++) {
                 if (i % stride[0] == 0) {
@@ -10415,16 +10441,6 @@ test_dataset_vlen_io(void)
 
     TESTING_2("test cleanup");
 
-    if (H5Fclose(file_id) < 0)
-        TEST_ERROR;
-    if (H5Gclose(container_group) < 0)
-        TEST_ERROR;
-    if (H5Dclose(dset_int) < 0)
-        TEST_ERROR;
-    if (H5Dclose(dset_float) < 0)
-        TEST_ERROR;
-    if (H5Dclose(dset_string) < 0)
-        TEST_ERROR;
     if (H5Sclose(space_id) < 0)
         TEST_ERROR;
 
@@ -10450,15 +10466,16 @@ test_dataset_vlen_io(void)
         TEST_ERROR;
     if (H5Tclose(vlen_string) < 0)
         TEST_ERROR;
-
+    if (H5Gclose(container_group) < 0)
+        TEST_ERROR;
+    if (H5Fclose(file_id) < 0)
+        TEST_ERROR;
     PASSED();
     return 0;
 error:
 
     H5E_BEGIN_TRY
     {
-        H5Fclose(file_id);
-        H5Gclose(container_group);
         if (dset_int != H5I_INVALID_HID)
             H5Dclose(dset_int);
         if (dset_float != H5I_INVALID_HID)
@@ -10482,6 +10499,8 @@ test_dataset_vlen_io(void)
         H5Tclose(vlen_int);
         H5Tclose(vlen_float);
         H5Tclose(vlen_string);
+        H5Gclose(container_group);
+        H5Fclose(file_id);
     }
     H5E_END_TRY
 
@@ -10513,7 +10532,8 @@ test_dataset_set_extent_chunked_unlimited(void)
 
     /* Make sure the connector supports the API functions being tested */
     if (!(vol_cap_flags_g & H5VL_CAP_FLAG_FILE_BASIC) || !(vol_cap_flags_g & H5VL_CAP_FLAG_GROUP_BASIC) ||
-        !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_BASIC) || !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_MORE)) {
+        !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_BASIC) || !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_MORE) ||
+        !(vol_cap_flags_g & H5VL_CAP_FLAG_DATASET_MORE)) {
         SKIPPED();
         printf("    API functions for basic file, group, basic or more dataset aren't supported with this "
                "connector\n");