diff --git a/R/cpp11.R b/R/cpp11.R
index 504a97ac..018cbd6a 100644
--- a/R/cpp11.R
+++ b/R/cpp11.R
@@ -196,6 +196,6 @@ cpp_monty_random_n_multinomial <- function(n_samples, r_size, r_prob, ptr) {
   .Call(`_monty_cpp_monty_random_n_multinomial`, n_samples, r_size, r_prob, ptr)
 }
 
-test_xoshiro_run <- function(obj, algorithm) {
-  .Call(`_monty_test_xoshiro_run`, obj, algorithm)
+test_xoshiro_run <- function(ptr) {
+  .Call(`_monty_test_xoshiro_run`, ptr)
 }
diff --git a/src/cpp11.cpp b/src/cpp11.cpp
index 5c3a7f3e..6348c5cb 100644
--- a/src/cpp11.cpp
+++ b/src/cpp11.cpp
@@ -352,10 +352,10 @@ extern "C" SEXP _monty_cpp_monty_random_n_multinomial(SEXP n_samples, SEXP r_siz
   END_CPP11
 }
 // test_rng.cpp
-std::vector<std::string> test_xoshiro_run(cpp11::sexp obj, std::string algorithm);
-extern "C" SEXP _monty_test_xoshiro_run(SEXP obj, SEXP algorithm) {
+std::vector<std::string> test_xoshiro_run(cpp11::sexp ptr);
+extern "C" SEXP _monty_test_xoshiro_run(SEXP ptr) {
   BEGIN_CPP11
-    return cpp11::as_sexp(test_xoshiro_run(cpp11::as_cpp<cpp11::decay_t<cpp11::sexp>>(obj), cpp11::as_cpp<cpp11::decay_t<std::string>>(algorithm)));
+    return cpp11::as_sexp(test_xoshiro_run(cpp11::as_cpp<cpp11::decay_t<cpp11::sexp>>(ptr)));
   END_CPP11
 }
 
@@ -410,7 +410,7 @@ static const R_CallMethodDef CallEntries[] = {
     {"_monty_cpp_monty_rng_set_state",                   (DL_FUNC) &_monty_cpp_monty_rng_set_state,                   2},
     {"_monty_cpp_monty_rng_state",                       (DL_FUNC) &_monty_cpp_monty_rng_state,                       1},
     {"_monty_monty_rng_alloc",                           (DL_FUNC) &_monty_monty_rng_alloc,                           3},
-    {"_monty_test_xoshiro_run",                          (DL_FUNC) &_monty_test_xoshiro_run,                          2},
+    {"_monty_test_xoshiro_run",                          (DL_FUNC) &_monty_test_xoshiro_run,                          1},
     {NULL, NULL, 0}
 };
 }
diff --git a/tests/testthat/test-rng.R b/tests/testthat/test-rng.R
index d2365cb7..15fee6f6 100644
--- a/tests/testthat/test-rng.R
+++ b/tests/testthat/test-rng.R
@@ -333,6 +333,18 @@ test_that("rexp agrees with stats::rexp", {
 })
 
 
+
+test_that("can sample from exponential distribution (mean)", {
+  r1 <- monty_rng_create(seed = 42)
+  r2 <- monty_rng_create(seed = 42)
+  expect_equal(monty_random_exponential_mean(0.5, r1),
+               monty_random_exponential_rate(2, r2))
+  expect_equal(monty_random_n_exponential_mean(10, 0.5, r1),
+               monty_random_n_exponential_rate(10, 2, r2))
+})
+
+
+
 test_that("continue stream", {
   rng1 <- monty_rng_create(seed = 1)
   rng2 <- monty_rng_create(seed = 1)
@@ -1070,6 +1082,9 @@ test_that("negative_binomial_mu follows from negative_binomial_prob", {
   prob <- 0.3
   size <- 20
   mu <- size * (1 - prob) / prob
+  expect_identical(
+    monty_random_negative_binomial_mu(size, mu, rng1),
+    monty_random_negative_binomial_prob(size, prob, rng2))
   expect_identical(
     monty_random_n_negative_binomial_mu(100, size, mu, rng1),
     monty_random_n_negative_binomial_prob(100, size, prob, rng2))
@@ -1125,6 +1140,9 @@ test_that("beta_binomial_prob follows from beta_binomial_ab", {
   b <- 5
   prob <- a / (a + b)
   rho <- 1 / (a + b + 1)
+  expect_identical(
+    monty_random_beta_binomial_prob(size, prob, rho, rng1),
+    monty_random_beta_binomial_ab(size, a, b, rng2))
   expect_identical(
     monty_random_n_beta_binomial_prob(100, size, prob, rho, rng1),
     monty_random_n_beta_binomial_ab(100, size, a, b, rng2))