diff --git a/.Rbuildignore b/.Rbuildignore
index 286e081..833658c 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -3,7 +3,7 @@
 ^LICENSE\.md$
 ^\.github$
 ^README\.Rmd$
-^man/universe_query\.Rd$
 ^_pkgdown\.yml$
 ^docs$
 ^pkgdown$
+^man/universe_query\.Rd$
diff --git a/DESCRIPTION b/DESCRIPTION
index b428730..60b385a 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -13,7 +13,8 @@ Depends:
     R (>= 4.2.0)
 Imports: 
     cli,
-    httr2
+    httr2,
+    rlang
 URL: https://docs.ropensci.org/starchart/, https://github.com/ropenscilabs/starchart
 BugReports: https://github.com/ropenscilabs/starchart/issues
 Config/Needs/build: moodymudskipper/devtag
diff --git a/R/global-search.R b/R/global-search.R
index 3c44a2f..4c546a3 100644
--- a/R/global-search.R
+++ b/R/global-search.R
@@ -10,6 +10,8 @@
 #' global_search(query = '"weather data"', limit = 1)
 #' global_search(query = 'needs:httr2', limit = 1)
 global_search <- function(query, limit = 100) {
+  assert_character(query, "query")
+
   httr2::request("https://r-universe.dev") |>
     httr2::req_url_path("api") |>
     httr2::req_url_path_append("search") |>
diff --git a/R/universe.R b/R/universe.R
index a9344e5..a13dad4 100644
--- a/R/universe.R
+++ b/R/universe.R
@@ -10,9 +10,7 @@
 #' universe_ls("ropensci")
 #' @family universe
 universe_ls <- function(universe) {
-  if (!is.character(universe) || length(universe) != 1) {
-    cli::cli_abort("{.arg universe} must be a character of length 1.")
-  }
+  assert_character(universe, "universe")
   # TODO assert that universe is an universe
 
   universe_query(
@@ -35,9 +33,7 @@ universe_ls <- function(universe) {
 #' universe_packages("ropensci")
 #' @family universe
 universe_packages <- function(universe, limit = 100) {
-  if (!is.character(universe) || length(universe) != 1) {
-    cli::cli_abort("{.arg universe} must be a character of length 1.")
-  }
+  assert_character(universe, "universe")
   # TODO assert that universe is an universe
 
   universe_query(
@@ -60,9 +56,8 @@ universe_packages <- function(universe, limit = 100) {
 #' universe_package("jeroen", package = "curl")
 #' @family universe
 universe_package <- function(universe, package) {
-  if (!is.character(universe) || length(universe) != 1) {
-    cli::cli_abort("{.arg universe} must be a character of length 1.")
-  }
+  assert_character(universe, "universe")
+  assert_character(package, "package")
   # TODO assert that universe is an universe
 
   if (!package %in% universe_ls(universe)) {
@@ -90,12 +85,8 @@ universe_package <- function(universe, package) {
 #' universe_search("ropensci", query = 'needs:httr2')
 #' @family universe
 universe_search <- function(universe, query, limit) {
-  if (!is.character(universe) || length(universe) != 1) {
-    cli::cli_abort("{.arg universe} must be a character of length 1.")
-  }
-  if (!is.character(query) || length(query) != 1) {
-    cli::cli_abort("{.arg query} must be a character of length 1.")
-  }
+  assert_character(universe, "universe")
+  assert_character(query, "query")
   # TODO assert that universe is an universe
 
   universe_query(
diff --git a/R/utils.R b/R/utils.R
index 97c08bc..d6b90f1 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -20,3 +20,9 @@ universe_query <- function(universe_url, path, query_params = NULL) {
   httr2::req_perform(request) |>
     httr2::resp_body_json()
 }
+
+assert_character <- function(x, name, call = rlang::caller_env()) {
+  if (!is.character(x) || length(x) != 1) {
+    cli::cli_abort("{.arg name} must be a character of length 1.", call = call)
+  }
+}
diff --git a/tests/testthat/_snaps/utils.md b/tests/testthat/_snaps/utils.md
new file mode 100644
index 0000000..0acbe0d
--- /dev/null
+++ b/tests/testthat/_snaps/utils.md
@@ -0,0 +1,13 @@
+# assert_character() works
+
+    Code
+      assert_character(1, "universe")
+    Condition
+      Error:
+      ! `name` must be a character of length 1.
+    Code
+      assert_character(c("bla", "blop"), "universe")
+    Condition
+      Error:
+      ! `name` must be a character of length 1.
+
diff --git a/tests/testthat/test-utils.R b/tests/testthat/test-utils.R
new file mode 100644
index 0000000..54435b5
--- /dev/null
+++ b/tests/testthat/test-utils.R
@@ -0,0 +1,6 @@
+test_that("assert_character() works", {
+  expect_snapshot(error = TRUE, {
+    assert_character(1, "universe")
+    assert_character(c("bla", "blop"), "universe")
+  })
+})