Guard undefined hyperspherical mean directions

tests/distributions/test_abstract_hyperspherical_distribution.py

@@ -7,6 +7,7 @@
 from pyrecest.backend import array, linalg, log, pi, sqrt
 from pyrecest.distributions import (
     AbstractHypersphericalDistribution,
+    HypersphericalUniformDistribution,
     VonMisesFisherDistribution,
 )
 
@@ -68,6 +69,16 @@ def test_mean_direction_numerical(self):
         vmf = VonMisesFisherDistribution(mu, kappa)
         self.assertLess(linalg.norm(vmf.mean_direction_numerical() - mu), 1e-6)
 
+    @unittest.skipIf(
+        pyrecest.backend.__backend_name__ == "jax",
+        reason="Not supported on this backend",
+    )
+    def test_mean_direction_numerical_undefined_for_uniform_circle(self):
+        """Tests that undefined mean directions are reported explicitly."""
+        uniform_circle = HypersphericalUniformDistribution(1)
+        with self.assertRaisesRegex(ValueError, "Mean direction is undefined"):
+            uniform_circle.mean_direction_numerical()
+
     def test_plotting_error_free_1d(self):
         """Tests the plotting function for circular distributions."""