diff --git a/R/ard_stats_poisson_test.R b/R/ard_stats_poisson_test.R
index bfd8868f..1fb3bcc1 100644
--- a/R/ard_stats_poisson_test.R
+++ b/R/ard_stats_poisson_test.R
@@ -15,8 +15,7 @@
 #' @param conf.level (scalar `numeric`)\cr
 #'   confidence level for confidence interval. Default is `0.95`.
 #' @param na.rm (scalar `logical`)\cr
-#'   whether missing values should be removed before summing the numerator and the denominator. Default
-#'   is `TRUE`.
+#'   whether missing values should be removed before summing the numerator and the denominator. Default is `TRUE`.
 #' @param ... arguments passed to [poisson.test()].
 #' @return an ARD data frame of class 'card'
 #' @name ard_stats_poisson_test
@@ -124,7 +123,8 @@ ard_stats_poisson_test <- function(data, numerator, denominator, na.rm = TRUE, b
       formals = formals(asNamespace("stats")[["poisson.test"]]),
       passed_args = dots_list(...),
       lst_ard_columns = list(context = "stats_poisson_test")
-    )
+    ) |>
+    dplyr::distinct()
 
   # rename "r" statistic to "mu"
   ret$stat_name[ret$stat_name == "r"] <- "mu"
diff --git a/man/ard_stats_poisson_test.Rd b/man/ard_stats_poisson_test.Rd
index 6ccc4d5f..ee6f5031 100644
--- a/man/ard_stats_poisson_test.Rd
+++ b/man/ard_stats_poisson_test.Rd
@@ -25,8 +25,7 @@ name of the event variable to be summed for computing the numerator.}
 name of the time variable to be summed for computing the denominator.}
 
 \item{na.rm}{(scalar \code{logical})\cr
-whether missing values should be removed before summing the numerator and the denominator. Default
-is \code{TRUE}.}
+whether missing values should be removed before summing the numerator and the denominator. Default is \code{TRUE}.}
 
 \item{by}{(\code{\link[dplyr:dplyr_tidy_select]{tidy-select}})\cr
 optional column name to compare by.}
diff --git a/tests/testthat/_snaps/ard_stats_poisson_test.md b/tests/testthat/_snaps/ard_stats_poisson_test.md
new file mode 100644
index 00000000..1f710740
--- /dev/null
+++ b/tests/testthat/_snaps/ard_stats_poisson_test.md
@@ -0,0 +1,8 @@
+# ard_stats_poisson_test() errors are handled correctly
+
+    Code
+      ard_stats_poisson_test(cards::ADTTE, by = TRTA, numerator = CNSR, denominator = AVAL)
+    Condition
+      Error in `ard_stats_poisson_test()`:
+      ! The `by` argument must have a maximum of two levels.
+
diff --git a/tests/testthat/test-ard_stats_poisson_test.R b/tests/testthat/test-ard_stats_poisson_test.R
new file mode 100644
index 00000000..20bf384c
--- /dev/null
+++ b/tests/testthat/test-ard_stats_poisson_test.R
@@ -0,0 +1,81 @@
+skip_if_not(is_pkg_installed("broom", reference_pkg = "cardx"))
+
+test_that("ard_stats_poisson_test() works for one sample tests", {
+  # Default values work
+  expect_silent(
+    ard_stats_poisson_test(cards::ADTTE, numerator = CNSR, denominator = AVAL)
+  )
+
+  # Custom values work
+  expect_silent(
+    ard_single <- ard_stats_poisson_test(
+      cards::ADTTE,
+      numerator = "CNSR",
+      denominator = "AVAL",
+      conf.level = 0.90,
+      r = 0.8,
+      alternative = "greater"
+    )
+  )
+
+  # Statistics calculated correctly
+  expect_equal(
+    ard_single |>
+      cards::get_ard_statistics(
+        stat_name %in%
+          c("estimate", "statistic", "p.value", "parameter", "conf.low", "conf.high", "method", "alternative")
+      ),
+    poisson.test(
+      x = sum(cards::ADTTE$CNSR),
+      T = sum(cards::ADTTE$AVAL),
+      r = 0.8,
+      conf.level = 0.9,
+      alternative = "greater"
+    ) |>
+      broom::tidy() |>
+      unclass(),
+    ignore_attr = TRUE
+  )
+})
+
+test_that("ard_stats_poisson_test() works for two sample tests", {
+  expect_silent(
+    ard_compare <-
+      cards::ADTTE |>
+      dplyr::filter(TRTA %in% c("Placebo", "Xanomeline High Dose")) |>
+      ard_stats_poisson_test(by = TRTA, numerator = CNSR, denominator = AVAL)
+  )
+
+  # Statistics calculated correctly
+  expect_equal(
+    ard_compare |>
+      cards::get_ard_statistics(
+        stat_name %in%
+          c("estimate", "statistic", "p.value", "parameter", "conf.low", "conf.high", "method", "alternative")
+      ),
+    poisson.test(
+      x = cards::ADTTE |>
+        dplyr::filter(TRTA %in% c("Placebo", "Xanomeline High Dose")) |>
+        dplyr::group_by(TRTA) |>
+        dplyr::summarise(sum = sum(CNSR)) |>
+        dplyr::pull(sum),
+      T = cards::ADTTE |>
+        dplyr::filter(TRTA %in% c("Placebo", "Xanomeline High Dose")) |>
+        dplyr::group_by(TRTA) |>
+        dplyr::summarise(sum = sum(AVAL)) |>
+        dplyr::pull(sum)
+    ) |>
+      broom::tidy() |>
+      unclass(),
+    ignore_attr = TRUE
+  )
+
+})
+
+test_that("ard_stats_poisson_test() errors are handled correctly", {
+  expect_snapshot(
+    cards::ADTTE |>
+      ard_stats_poisson_test(by = TRTA, numerator = CNSR, denominator = AVAL),
+    error = TRUE
+  )
+})