From 5f3a5e76ead444dff96bc6430e6378f5429435d2 Mon Sep 17 00:00:00 2001
From: Nicholas Bianco <nbianco@stanford.edu>
Date: Wed, 2 Oct 2024 09:29:24 -0700
Subject: [PATCH] Use WithinRel comparison for fiber stiffness since were using
 a finite-differenced estimate

---
 .../Actuators/Test/testDeGrooteFregly2016Muscle.cpp    | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/OpenSim/Actuators/Test/testDeGrooteFregly2016Muscle.cpp b/OpenSim/Actuators/Test/testDeGrooteFregly2016Muscle.cpp
index d69788f140..79f35cd9d1 100644
--- a/OpenSim/Actuators/Test/testDeGrooteFregly2016Muscle.cpp
+++ b/OpenSim/Actuators/Test/testDeGrooteFregly2016Muscle.cpp
@@ -634,8 +634,10 @@ TEST_CASE("DeGrooteFregly2016Muscle basics") {
             SimTK::Real fiberStiffnessAlongTendon =
                     diffFiberStiffnessAlongTendon.calcDerivative(
                             muscle.get_optimal_fiber_length());
-            CHECK(muscle.getFiberStiffnessAlongTendon(state) ==
-                    Approx(fiberStiffnessAlongTendon));
+            CAPTURE(muscle.getFiberStiffnessAlongTendon(state));
+            CAPTURE(fiberStiffnessAlongTendon);
+            CHECK_THAT(muscle.getFiberStiffnessAlongTendon(state),
+                    Catch::Matchers::WithinRel(fiberStiffnessAlongTendon, 1e-6));
 
             SimTK::Real tendonStiffness = SimTK::Infinity;
             CHECK(muscle.getTendonStiffness(state) == SimTK::Infinity);
@@ -643,11 +645,9 @@ TEST_CASE("DeGrooteFregly2016Muscle basics") {
                     tendonStiffness, fiberStiffnessAlongTendon);
             CAPTURE(muscleStiffness);
             CAPTURE(tendonStiffness);
-            CAPTURE(fiberStiffnessAlongTendon);
             CAPTURE(muscle.getTendonStiffness(state));
-            CAPTURE(muscle.getFiberStiffnessAlongTendon(state));
             CHECK_THAT(muscle.getMuscleStiffness(state),
-                    Catch::Matchers::WithinAbs(muscleStiffness, 1e-10));
+                    Catch::Matchers::WithinRel(muscleStiffness, 1e-6));
             CHECK_THAT(muscle.getFiberActivePower(state),
                     Catch::Matchers::WithinAbs(0.0, 1e-10));
             CHECK(muscle.getFiberPassivePower(state) ==