diff --git a/R/causal_idx.R b/R/causal_idx.R
index 6eccb7c..28a9fad 100644
--- a/R/causal_idx.R
+++ b/R/causal_idx.R
@@ -53,6 +53,8 @@ as_causal_idx <- function(x) {
 
 
 # printing
+# (tests skipped on CI)
+# nocov start
 #' @export
 format.causal_idx <- function(x, ...) {
     vapply(vctrs::vec_data(x), format_index_line, "")
@@ -60,6 +62,7 @@ format.causal_idx <- function(x, ...) {
 format_index_line <- function(y) {
     paste0("(", paste0(formatC(y[!is.na(y)]), collapse=","), ")")
 }
+# nocov end
 
 # vctrs -------------------------------------------------------------------
 
diff --git a/R/causal_mod.R b/R/causal_mod.R
index 0f8ec87..d37a1aa 100644
--- a/R/causal_mod.R
+++ b/R/causal_mod.R
@@ -35,7 +35,9 @@ new_causal_mod <- function(x = list(), fitted = double(0), idx = seq_along(fitte
 #'
 #' d <- rbind(NA, npk)
 #' m_mis <- lm(yield ~ block + N*P*K, data=d)
+#' fitted(m_mis) # length doesn't match rows of `d`
 #' causal_mod(m_mis) # NA for missing value
+#' attr(causal_mod(m_mis), "idx")
 #'
 #' @order 1
 #' @export
@@ -70,14 +72,17 @@ is_causal_mod <- function(x) {
 
 
 # printing
+# (tests skipped on CI)
+# nocov start
 #' @export
 format.causal_mod <- function(x, ...) {
     formatC(vctrs::vec_data(x))
 }
 #' @export
 str.causal_mod <- function(object, max.level=2, ...) {
-    NextMethod(max.level=max.level, ...) # nocov
+    NextMethod(max.level=max.level, ...)
 }
+# nocov end
 
 # vctrs -------------------------------------------------------------------
 
diff --git a/R/causal_tbl.R b/R/causal_tbl.R
index 4a72464..19f14a6 100644
--- a/R/causal_tbl.R
+++ b/R/causal_tbl.R
@@ -109,7 +109,8 @@ reconstruct.causal_tbl <- function(data, old) {
 #' that a `causal_tbl` has the necessary columns set via helpers like
 #' [has_treatment()], [has_outcome()], etc.
 #'
-#' @param ... passed on to [tibble()]
+#' @param ... passed on to [vctrs::df_list()] (for `causal_tbl` only) then
+#'   [vctrs::new_data_frame()] (both constructors).
 #' @param .outcome the column containing the outcome variable (tidy-selected).
 #'   Can be set later with [set_outcome()].
 #' @param .treatment the column containing the treatment variable (tidy-selected).
@@ -223,6 +224,8 @@ assert_df <- function(data, arg) {
 
 
 # Printing -----------------------------------------------------------------
+# (tests skipped on CI)
+# nocov start
 
 #' @importFrom pillar tbl_sum
 #' @method tbl_sum causal_tbl
@@ -278,3 +281,5 @@ ctl_new_pillar.causal_tbl <- function(controller, x, width, ..., title = NULL) {
         data = out$data
     ))
 }
+
+# nocov end
diff --git a/man/causal_mod.Rd b/man/causal_mod.Rd
index 93977f3..6e6f2fc 100644
--- a/man/causal_mod.Rd
+++ b/man/causal_mod.Rd
@@ -49,6 +49,8 @@ causal_mod(m)
 
 d <- rbind(NA, npk)
 m_mis <- lm(yield ~ block + N*P*K, data=d)
+fitted(m_mis) # length doesn't match rows of `d`
 causal_mod(m_mis) # NA for missing value
+attr(causal_mod(m_mis), "idx")
 
 }
diff --git a/man/causal_tbl.Rd b/man/causal_tbl.Rd
index 84cbb5f..74e7150 100644
--- a/man/causal_tbl.Rd
+++ b/man/causal_tbl.Rd
@@ -16,7 +16,8 @@ as_causal_tbl(x)
 is_causal_tbl(x)
 }
 \arguments{
-\item{...}{passed on to \code{\link[=tibble]{tibble()}}}
+\item{...}{passed on to \code{\link[vctrs:df_list]{vctrs::df_list()}} (for \code{causal_tbl} only) then
+\code{\link[vctrs:new_data_frame]{vctrs::new_data_frame()}} (both constructors).}
 
 \item{.outcome}{the column containing the outcome variable (tidy-selected).
 Can be set later with \code{\link[=set_outcome]{set_outcome()}}.}
diff --git a/tests/testthat/test-causal_idx.R b/tests/testthat/test-causal_idx.R
index 313a5d9..41644d3 100644
--- a/tests/testthat/test-causal_idx.R
+++ b/tests/testthat/test-causal_idx.R
@@ -29,6 +29,9 @@ test_that("causal_idx slicing", {
 
 
 test_that("causal_idx printing", {
+    skip_on_ci()
+    skip_on_cran()
+
     idx <- causal_idx(list(2, c(1, NA, 3), 2))
 
     expect_snapshot(print(idx))
diff --git a/tests/testthat/test-causal_mod.R b/tests/testthat/test-causal_mod.R
index e0f9a2d..0da387a 100644
--- a/tests/testthat/test-causal_mod.R
+++ b/tests/testthat/test-causal_mod.R
@@ -35,6 +35,9 @@ test_that("causal_mod slicing", {
 
 
 test_that("causal_mod printing", {
+    skip_on_ci()
+    skip_on_cran()
+
     m <- lm(yield ~ block + N*P*K, data=npk)
     x <- causal_mod(m)
 
diff --git a/tests/testthat/test-causal_tbl.R b/tests/testthat/test-causal_tbl.R
index caad879..29b1db0 100644
--- a/tests/testthat/test-causal_tbl.R
+++ b/tests/testthat/test-causal_tbl.R
@@ -98,6 +98,9 @@ test_that("causal_tbl slicing and renaming", {
 })
 
 test_that("causal_tbl printing", {
+    skip_on_ci()
+    skip_on_cran()
+
     x <- causal_tbl(milk_first = c(0, 1, 0, 1, 1, 0, 0, 1),
                     guess = c(0, 1, 0, 1, 1, 0, 0, 1),
                     .outcome = guess,