diff --git a/R/brm_marginal_summaries.R b/R/brm_marginal_summaries.R
index 1b4d4c4b..086f40a7 100644
--- a/R/brm_marginal_summaries.R
+++ b/R/brm_marginal_summaries.R
@@ -31,15 +31,18 @@
 #'   for the credible intervals.
 #' @examples
 #' set.seed(0L)
-#' sim <- brm_simulate()
-#' data <- sim$data
+#' data <- brm_data(
+#'   data = tibble::as_tibble(brm_simulate()$data),
+#'   outcome = "response",
+#'   role = "response",
+#'   group = "group",
+#'   time = "time",
+#'   patient = "patient"
+#' )
 #' data$group <- paste("treatment", data$group)
 #' data$time <- paste("visit", data$time)
 #' formula <- brm_formula(
-#'   response = "response",
-#'   group = "group",
-#'   time = "time",
-#'   patient = "patient",
+#'   data = data,
 #'   effect_base = FALSE,
 #'   interaction_base = FALSE
 #' )
@@ -58,12 +61,9 @@
 #' )
 #' draws <- brm_marginal_draws(
 #'   model = model,
-#'   group = "group",
-#'   time = "time",
-#'   patient = "patient",
+#'   data = data,
 #'   control = "treatment 1",
-#'   baseline = "visit 1",
-#'   outcome = "response"
+#'   baseline = "visit 1"
 #' )
 #' suppressWarnings(brm_marginal_summaries(draws))
 brm_marginal_summaries <- function(
diff --git a/tests/testthat/test-brm_marginal_summaries.R b/tests/testthat/test-brm_marginal_summaries.R
index 7b475a93..23587804 100644
--- a/tests/testthat/test-brm_marginal_summaries.R
+++ b/tests/testthat/test-brm_marginal_summaries.R
@@ -1,18 +1,17 @@
 test_that("brm_marginal_summaries() on response", {
   set.seed(0L)
-  sim <- brm_simulate(
-    n_group = 2L,
-    n_patient = 100L,
-    n_time = 4L
+  data <- brm_data(
+    data = tibble::as_tibble(brm_simulate()$data),
+    outcome = "response",
+    role = "response",
+    group = "group",
+    time = "time",
+    patient = "patient"
   )
-  data <- sim$data
   data$group <- paste("treatment", data$group)
   data$time <- paste("visit", data$time)
   formula <- brm_formula(
-    response = "response",
-    group = "group",
-    time = "time",
-    patient = "patient",
+    data = data,
     effect_base = FALSE,
     interaction_base = FALSE
   )
@@ -31,12 +30,9 @@ test_that("brm_marginal_summaries() on response", {
   )
   draws <- brm_marginal_draws(
     model = model,
-    group = "group",
-    time = "time",
-    patient = "patient",
+    data = data,
     control = "treatment 1",
-    baseline = "visit 1",
-    outcome = "response"
+    baseline = "visit 1"
   )
   suppressWarnings(
     x <- brm_marginal_summaries(
@@ -125,19 +121,18 @@ test_that("brm_marginal_summaries() on response", {
 
 test_that("brm_marginal_summaries() on change", {
   set.seed(0L)
-  sim <- brm_simulate(
-    n_group = 2L,
-    n_patient = 100L,
-    n_time = 4L
+  data <- brm_data(
+    data = tibble::as_tibble(brm_simulate()$data),
+    outcome = "response",
+    role = "change",
+    group = "group",
+    time = "time",
+    patient = "patient"
   )
-  data <- sim$data
   data$group <- paste("treatment", data$group)
   data$time <- paste("visit", data$time)
   formula <- brm_formula(
-    response = "response",
-    group = "group",
-    time = "time",
-    patient = "patient",
+    data = data,
     effect_base = FALSE,
     interaction_base = FALSE
   )
@@ -156,12 +151,9 @@ test_that("brm_marginal_summaries() on change", {
   )
   draws <- brm_marginal_draws(
     model = model,
-    group = "group",
-    time = "time",
-    patient = "patient",
+    data = data,
     control = "treatment 1",
-    baseline = "visit 1",
-    outcome = "change"
+    baseline = "visit 1"
   )
   suppressWarnings(
     x <- brm_marginal_summaries(