From 8a3ac66b3ff2a60ab4336d1bbc14f0121906a08a Mon Sep 17 00:00:00 2001
From: "mergify[bot]" <37929162+mergify[bot]@users.noreply.github.com>
Date: Wed, 14 Aug 2024 11:56:10 +0100
Subject: [PATCH] Fix flaky transmission_interface tests by making them
 deterministic. (backport #1665) (#1670)

---
 .../four_bar_linkage_transmission.hpp                       | 2 +-
 transmission_interface/test/random_generator_utils.hpp      | 6 ++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/transmission_interface/include/transmission_interface/four_bar_linkage_transmission.hpp b/transmission_interface/include/transmission_interface/four_bar_linkage_transmission.hpp
index 39f5df6f61..863c20da9b 100644
--- a/transmission_interface/include/transmission_interface/four_bar_linkage_transmission.hpp
+++ b/transmission_interface/include/transmission_interface/four_bar_linkage_transmission.hpp
@@ -288,7 +288,7 @@ inline void FourBarLinkageTransmission::actuator_to_joint()
 
     joint_eff[0].set_value(jr[0] * act_eff[0].get_value() * ar[0]);
     joint_eff[1].set_value(
-      jr[1] * (act_eff[1].get_value() * ar[1] - act_eff[0].get_value() * ar[0] * jr[0]));
+      jr[1] * (act_eff[1].get_value() * ar[1] - jr[0] * act_eff[0].get_value() * ar[0]));
   }
 }
 
diff --git a/transmission_interface/test/random_generator_utils.hpp b/transmission_interface/test/random_generator_utils.hpp
index e6088f1b2f..01e1245e48 100644
--- a/transmission_interface/test/random_generator_utils.hpp
+++ b/transmission_interface/test/random_generator_utils.hpp
@@ -26,12 +26,14 @@ using std::vector;
 /// \brief Generator of pseudo-random double in the range [min_val, max_val].
 // NOTE: Based on example code available at:
 // http://stackoverflow.com/questions/2860673/initializing-a-c-vector-to-random-values-fast
+// Use a user specified seed instead of system time for deterministic tests
 struct RandomDoubleGenerator
 {
 public:
-  RandomDoubleGenerator(double min_val, double max_val) : min_val_(min_val), max_val_(max_val)
+  RandomDoubleGenerator(double min_val, double max_val, unsigned int seed = 1234)
+  : min_val_(min_val), max_val_(max_val)
   {
-    srand(time(nullptr));
+    srand(seed);
   }
   double operator()()
   {