diff --git a/tests/testthat/test-utils_join_coalesce.R b/tests/testthat/test-utils_join_coalesce.R
index 2cd9a1da..72e86bbb 100644
--- a/tests/testthat/test-utils_join_coalesce.R
+++ b/tests/testthat/test-utils_join_coalesce.R
@@ -3,10 +3,19 @@ test_that("join coalesce function works", {
   x <- data.frame(id1 = c(NA_character_,letters[1:4]), a = c(1,NA,3,NA,5), b = 1:5 * 10)
   y <- data.frame(id2 = c(letters[3:11],NA_character_), a = -(1:10), c = 1:10 * 100)
 
-  left1 <- join_coalesce(x,y, by = c("id1"="id2"))
-  left2 <- join_coalesce(x,y, by.x = "id1", by.y = "id2")
-  inner1 <- join_coalesce(x,y, by = c("id1"="id2"), type = "inner")
-  full1 <- join_coalesce(x,y, by = c("id1"="id2"), type = "full")
+  # Keys include NAs and trigger a warning
+  expect_warning(
+    left1 <- join_coalesce(x, y, by = c("id1" = "id2"))
+  )
+  expect_warning(
+    left2 <- join_coalesce(x, y, by.x = "id1", by.y = "id2")
+  )
+  expect_warning(
+    inner1 <- join_coalesce(x, y, by = c("id1" = "id2"), type = "inner")
+  )
+  expect_warning(
+    full1 <- join_coalesce(x, y, by = c("id1" = "id2"), type = "full")
+  )
 
   expect_equal(left1,left2) # both join-by methods work the same
   expect_equal(sum(is.na(left1$a)), 1) # one NA on left join