From 1b6ffe5029b0cb9ee65fc5685e62bf11b8ad7f6c Mon Sep 17 00:00:00 2001
From: gowerc <craig.gower-page@roche.com>
Date: Mon, 5 Feb 2024 16:26:06 +0000
Subject: [PATCH] Ensure alpha < beta for uniform prior

---
 R/Prior.R                   | 4 ++++
 tests/testthat/test-Prior.R | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/R/Prior.R b/R/Prior.R
index 1a7d4300..8ef9f09a 100755
--- a/R/Prior.R
+++ b/R/Prior.R
@@ -364,6 +364,10 @@ prior_none <- function() {
 #'
 #' @export
 prior_uniform <- function(alpha, beta) {
+    assert_that(
+        alpha < beta,
+        msg = "`alpha`` must be less than `beta`"
+    )
     Prior(
         parameters = list(alpha = alpha, beta = beta),
         display = "uniform(alpha = {alpha}, beta = {beta})",
diff --git a/tests/testthat/test-Prior.R b/tests/testthat/test-Prior.R
index 4266d441..e5536f34 100644
--- a/tests/testthat/test-Prior.R
+++ b/tests/testthat/test-Prior.R
@@ -130,6 +130,11 @@ test_that("Invalid prior parameters are rejected", {
         regexp = "Invalid.*`beta`"
     )
 
+    expect_error(
+        prior_uniform(10, 9),
+        regexp = "`alpha`` must be less than `beta`"
+    )
+
 
     # Ensure that validation doesn't wrongly reject priors with no user specified parameters
     expect_s4_class(prior_none(), "Prior")