Add more tests for Sphere class

boule/tests/test_sphere.py

@@ -72,6 +72,23 @@ def test_check_geocentric_grav_const():
         assert len(warn) >= 1
 
 
+def test_normal_gravity_computed_on_internal_point(sphere):
+    """
+    Check if warn is raised if height is negative for normal_gravity,
+    normal_gravity_potential, and normal_gravitational_potential.
+    """
+    latitude = np.linspace(-90, 90, 100)
+    with warnings.catch_warnings(record=True) as warn:
+        sphere.normal_gravity(latitude, height=-10)
+        assert len(warn) >= 1
+    with warnings.catch_warnings(record=True) as warn:
+        sphere.normal_gravity_potential(latitude, height=-10)
+        assert len(warn) >= 1
+    with warnings.catch_warnings(record=True) as warn:
+        sphere.normal_gravitational_potential(latitude, height=-10)
+        assert len(warn) >= 1
+
+
 @pytest.mark.parametrize("si_units", [False, True], ids=["mGal", "SI"])
 def test_normal_gravity_pole_equator(sphere, si_units):
     """