diff --git a/tests/testthat/_snaps/misc.md b/tests/testthat/_snaps/misc.md
index ae66946c..f14e4982 100644
--- a/tests/testthat/_snaps/misc.md
+++ b/tests/testthat/_snaps/misc.md
@@ -70,3 +70,13 @@
       Error:
       ! `inclusive` must be a logical vector of length 2, not an integer vector.
 
+# vctrs-helpers-parameters
+
+    Code
+      dials:::df_size(2)
+    Condition
+      Error in `dials:::df_size()`:
+      ! Cannot get the df size of a non-list.
+      i This is an internal error that was detected in the dials package.
+        Please report it at <https://github.com/tidymodels/dials/issues> with a reprex (<https://tidyverse.org/help/>) and the full backtrace.
+
diff --git a/tests/testthat/_snaps/space_filling.md b/tests/testthat/_snaps/space_filling.md
index 5a5aabdc..1079463e 100644
--- a/tests/testthat/_snaps/space_filling.md
+++ b/tests/testthat/_snaps/space_filling.md
@@ -22,6 +22,17 @@
       x This argument contains unknowns: `mtry`.
       i See the `dials::finalize()` function.
 
+---
+
+    Code
+      grid_max_entropy(mixture(), levels = 11)
+    Condition
+      Warning:
+      `levels` is not an argument to `grid_max_entropy()`.
+      i Did you mean `size`?
+      Error in `parameters()`:
+      ! The objects should all be <param> objects.
+
 # `grid_latin_hypercube()` is deprecated
 
     Code
@@ -46,6 +57,17 @@
       x This argument contains unknowns: `mtry`.
       i See the `dials::finalize()` function.
 
+---
+
+    Code
+      grid_latin_hypercube(mixture(), levels = 11)
+    Condition
+      Warning:
+      `levels` is not an argument to `grid_latin_hypercube()`.
+      i Did you mean `size`?
+      Error in `parameters()`:
+      ! The objects should all be <param> objects.
+
 # S3 methods for space-filling
 
     Code
diff --git a/tests/testthat/test-misc.R b/tests/testthat/test-misc.R
index d4046e65..e89dad45 100644
--- a/tests/testthat/test-misc.R
+++ b/tests/testthat/test-misc.R
@@ -53,3 +53,12 @@ test_that("check_inclusive()", {
   expect_snapshot(error = TRUE, check_inclusive(c(TRUE, NA)))
   expect_snapshot(error = TRUE, check_inclusive(1:2))
 })
+
+
+test_that("vctrs-helpers-parameters", {
+  expect_false(dials:::is_parameters(2))
+  expect_snapshot(
+    error = TRUE,
+    dials:::df_size(2)
+  )
+})
diff --git a/tests/testthat/test-space_filling.R b/tests/testthat/test-space_filling.R
index 511ce560..282352d9 100644
--- a/tests/testthat/test-space_filling.R
+++ b/tests/testthat/test-space_filling.R
@@ -31,6 +31,15 @@ test_that("max entropy designs", {
   )
   expect_equal(ncol(grid_3), 1L)
 
+  grid_4 <- grid_max_entropy(
+    list(cost = cost(), mix = mixture()),
+    size = 11,
+    original = FALSE
+  )
+  expect_equal(nrow(grid_4), 11L)
+  expect_true(all(grid_4$mix > 0 & grid_4$mix < 1))
+  expect_true(all(grid_4$cost > -10 & grid_4$cost < 5))
+
   expect_snapshot(
     error = TRUE,
     grid_max_entropy(
@@ -39,6 +48,14 @@ test_that("max entropy designs", {
       original = FALSE
     )
   )
+
+  expect_snapshot(
+    error = TRUE,
+    grid_max_entropy(
+      mixture(),
+      levels = 11
+    )
+  )
 })
 
 test_that("`grid_latin_hypercube()` is deprecated", {
@@ -74,6 +91,15 @@ test_that("latin square designs", {
   )
   expect_equal(ncol(grid_3), 1L)
 
+  grid_4 <- grid_latin_hypercube(
+    list(cost = cost(), mix = mixture()),
+    size = 11,
+    original = FALSE
+  )
+  expect_equal(nrow(grid_4), 11L)
+  expect_true(all(grid_4$mix > 0 & grid_4$mix < 1))
+  expect_true(all(grid_4$cost > -10 & grid_4$cost < 5))
+
   expect_lt(
     nrow(grid_latin_hypercube(prod_degree(), prune_method(), size = 20)),
     20
@@ -87,6 +113,14 @@ test_that("latin square designs", {
       original = FALSE
     )
   )
+
+  expect_snapshot(
+    error = TRUE,
+    grid_latin_hypercube(
+      mixture(),
+      levels = 11
+    )
+  )
 })